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Farmers' Bulletin No. 2082 



Locating a commercial greenhouse. 1 

Types of greenhouses 2 

Internal features of greenhouse 3 

Systems of watering 3 

Ground beds 4 

Essential walks 4 

Cropping plans commonly used 4 

Suitable soils and their modifica- 
tion 5 

Preparing the soil for plant- 
ing 6 

Chemical fertilizers 6 

Varieties of greenhouse tomatoes. 8 

Descriptions 8 

Growing tomato plants for green- 
house crops 9 

Providing sufficient seed and 

plants 10 

Time for sowing seed 10 

Methods used for starting 

seedlings 10 

Growing the planting stock, _ 11 
When and how to set plants. _ 13 
Importance of control of soil mois- 
ture 15 

Maintaining proper temperature 

range and ventilation 15 

Cultivation 16 

Training and pruning 16 



Pollination 18 

Mechanical methods 20 

Chemical treatments 21 

Diseases 22 

Nematode injury 22 

Recommendations for con- 
trol 24 

Insects and other pests 24 

Greenhouse whitefly 26 

Aphids * 26 

Two-spotted spider mites 26 

Thrips 26 

Garden centipede 26 

Corn ear worm 27 

Mealybugs 27 

Tomato pin worm 27 

Tomato russet mite 27 

Armyworms 27 

Cutworms 28 

Cabbage loopers 28 

Greenhouse leaf tier 28 

Control measures for small 

greenhouses 28 

Sanitation 28 

Precautions 28 

Harvesting and marketing 29 

United States Standards for green- 
house tomatoes 30 

Washington, D. C. 

Issued May 1955 

For sale by tlie Superintendent of Documents. U. S. Government Printing Office 
Washington 25, D. C. - Price 15 cents 

Commercial Production of 


B .^ H ^^^ H ^^^^^ H ^_^^ HH __^__^^_^^___i By William S. Porte, 

pathologist, Horticultural Crops Research Branch, and Floyd F. Smith, principal 
entomologist, Entomology Research Branch, Agricultural Research Service 

Growing of tomatoes in green- 
houses is one of the most technical 
and intensive of agricultural enter- 
prises. It can also become one of 
the most profitable if the available 
technical information and the many 
facets of the art of growing green- 
house tomatoes are thoroughly 

The beginner should learn all he 
can about the effects of sunlight, 
heat, water, air, and soil on green- 
house tomatoes before assuming the 
responsibility for growing a crop. 
In addition to obtaining the advice 
of experienced agriculturists and 
studying the literature written on 
greenhouse culture, the beginner 
will gain valuable knowledge by 
working for a successful grower. 
After he has gained some experi- 
ence in growing hothouse tomatoes 
it is safer to build, buy, or rent a 
small greenhouse and accumulate 
the additional know-how essential 
for successful gradual expansion 
of the enterprise as profits seem to 

In 1950 nearly every State had 
some commercial greenhouses used 
for the production of vegetables. 
The most extensive development 
has been in the great industrial area 
north of the Ohio and east of the 
Mississippi Rivers. The largest 

commercial vegetable greenhouses 
are located in the environs of the 
following cities : Cleveland, Boston, 
Indianapolis, Cincinnati, Toledo, 
Terre Haute, Grand Rapids, and 
Milwaukee. In 1950 Ohio led the 
States with 650 acres under glass; 
followed by Indiana, 150 acres; 
Massachusetts, 100 acres; and 
Michigan, Illinois, New York, and 
Wisconsin, approximately 50 acres 
each. The rest of the States have 
around 1,000 additional acres of 
vegetables under glass. 

The three leading vegetable 
greenhouse crops grown in the 
United States are tomatoes, lettuce, 
and cucumbers. The wholesale 
market value of these hothouse 
vegetables in 1949 is shown in table 
1 for the 11 leading States and the 
totals for the whole country. The 
tomato is by far the most important 
glasshouse vegetable crop, with a 
gross annual wholesale value of 
more than $10 million. 


A greenhouse close to a good local 
market has a big advantage over a 
location far distant from markets. 
It not only saves much transporta- 
tion expense but reduces time in 
transit, enabling the grower to mar- 
ket the highest quality vine-ripened 

1 Supersedes Farmers' Bulletin 1431, Greenhouse Tomatoes. 


Table 1. — Annual wholesale market value of vegetables grown under 
glass in the United States in 191$ 1 





All nthpr 

TrofrDto V»l oca 
V CgC LdiUltJb 


$6, 803, 550 





SI 14 594 

Indiana _ __ _ 

yi4, o4z 





16, 241 

533, 161 





70, 553 

Illinois _ _ 

269, 660 





4, 928 


266, 295 





31, 679 


217, 320 





2, 643 

Wisconsin _ _ _ 

196, 253 





18, 032 

New York _ _ 

187, 422 





20, 175 

Missouri _ _ 

124, 153 







93, 219 






93, 150 



All others 

398, 673 





18, 880 

Total for United States, 

10, 077, 398 

1, 393, 


1, 277, 


298, 865 

1 Data compiled by Agricultural Marketing Service from U. S. Census of Agriculture, 

tomatoes. Fuel, water, and labor 
at reasonable cost are essential, and 
a fertile, medium-textured soil is 
an advantage. 

Clear air free from smoke and 
gases poisonous to plants and a rel- 
atively high percentage of sunshine 
during the short days of fall and 
winter are desirable. A site fully 
exposed to sunlight but protected 
from winds and storms by wind- 
breaks will save fuel and breakage 
of glass. However, many thriving 
greenhouse enterprises are located 
in areas subject to much cloudy 

The position of a greenhouse with 
reference to the points of the com- 
pass has little effect on growing to- 
matoes in this country. A north- 
south direction provides a more uni- 
form distribution of light through- 
out the year and enables the con- 
struction of headhouses at the north 
end of the range. In greenhouses 
constructed in an east-west direc- 
tion, crop rows running north and 
south provide better exposure to 
sunlight during short winter days. 

The greenhouse site should have 
good air and water drainage. Stale 

moisture-laden air favors tomato 
foliage diseases, especially leaf 
mold. Excess water from low situ- 
ations is often drained into concrete 
cisterns or ponds. Water collected 
from soil drainage should not be 
used to irrigate crops. This water 
may gradually increase the concen- 
trations of soluble salts in the soil 
and also tend to spread various dis- 
eases and pests. However, rain- 
water collected from roofs into a 
separate cistern is safe to use for 
irrigating crops. 


There are many types of green- 
houses — from the small shed roof 
"lean-to" houses constructed of 
wood-frame sash to the large mod- 
ern steel-frame houses with truss- 
supported roofs. Most new houses 
are of steel, wood, and masonry con- 
struction with even-spanned roofs 
( fig. 1 ) . These modern houses with 
6 feet or more of headroom at the 
eaves are the most satisfactory type 
for growing tomatoes. Standard 
plans and specifications for green- 
houses are available from manuf ac- 


Figure 1. — A medium-sized greenhouse unit of steel, tvood, and masonry eonstruction. 

hirers of this equipment, and the 
details of construction and heating 
are fully discussed in Farmers' Bul- 
letin 1318, Greenhouse Construction 
and Heating. 2 


Systems of Watering 

Water-supply pipes are usually 
placed underground, and short ver- 
tical pipes fitted with garden-hose 
faucets are attached at intervals so 
that any part of the house can be 
watered with 50 to 75 feet of garden 
hose. In most commercial estab- 
lishments, however, watering is 
done with hose only when the plants 
are first set out and their water re- 
quirements are relatively small. 
Many of the larger houses are 
equipped with a permanent system 
of pipes and nozzles for sprinkler 
irrigation either overhead or near 
the soil surface. 

Automatic watering machines or 
hose reels are now in limited use. 

These facilities cut labor costs. 

2 This and other Farmers' Bulletins 
listed are available free from the Office 
of Information, U. S. Department of Ag- 
riculture, Washington 25, 1). C. 

A skid with spray nozzles and hose 
attached is pulled to the end of the 
row and the machine winds the hose 
back up. 

Less frequently, subirrigation 
systems composed of lines of un- 
glazed agricultural tile are used. 
These are spaced 2 to 4 feet apart 
and laid end to end below plow 
depth and enable the greenhouse op- 
erator to water the plants without 
wetting the surface of the soil; 3- 
or 4-inch tile in 1-foot lengths laid 
with about one-quarter inch be- 
tween pieces is generally used. 

Each tile line is provided with 
an opening at both ends so water 
can be conducted into it from either 
end through garden hose until the 
soil is sufficiently irrigated. In 
tile lines more than 150 feet long, 
extra openings should be provided 
about every 100 feet so the soil will 
be more evenly moistened through- 
out the length of the bed. Opera- 
tors often use several lines of hose 
to water simultaneously, thereby 
saving much time. Sometimes per- 
manent installations of water pipes 
connected with the tile lines are used 
to speed up subirrigation. 

The tile may also be used to fa- 
cilitate steaming the soil. This 


may be accomplished by inserting a 
steampipe manifold into the open 
ends of the tile lines. All openings 
are then closed with burlap or rag 
plugs smeared over with clay mud. 
The subirrigation tile lines also 
provide extra soil aeration and 
drainage. Where permanent over- 
head or surface irrigation systems 
are used, tile are usually installed 
exclusively for steaming the soil. 

Ground Beds 

When tomatoes were first grown 
in greenhouses practically all the 

Elants were grown on raised 
enches, because it was thought that 
bottom heat under the benches was 
essential in order to obtain a good 
crop. Later it was learned that 
better crops could be grown at floor 
level in ground beds without any 
bottom heat. 

Ground beds are better than 
raised benches for tomatoes be- 
cause the soil can be more easily 
and economically prepared. Power 
machinery is often used in the 
larger houses. Tomato plants are 
tall growing, needing 6 feet or more 
for growth. Tomatoes growing in 
ground beds are easier to water, to 
train, and to harvest. The high 
cost of constructing and maintain- 
ing benches is now largely elimi- 
nated from greenhouse tomato 

Essential Walks 

Most permanent walks can be 
eliminated from tomato green- 
houses. Concrete or brick walks 
interfere with the use of power ma- 
chinery, make soil sanitation meas- 
ures less effective, and tend to re- 
duce the number of tomatoes that 
can be grown in each greenhouse 
unit. Essential temporary walks 
can be provided by board runways 
between certain rows of plants. 
These are picked up and stored as 
soon as the crop is harvested. Per- 

manent concrete walks that are 
necessary should be laid, wherever 
possible, next to heating lines where 
it is too hot for good plant growth. 


Many greenhouses are used for 
the production of two or more dif- 
ferent crops. Tomatoes, lettuce, 
and cucumbers are the three most 
important vegetable crops grown in 
greenhouses. These crops are used 
in various sequences and in combi- 
nation with other vegetable and 
flower crops. While no definite 
cropping plans suited to the needs 
of all growers located in different 
parts of the United States can be 
given, the crop sequences here sug- 
gested are used by many greenhouse 
growers in some important vege- 
table-forcing communities. 

Plan 1 

Tomatoes. — Seed sown July 1 to 15; 

plants set in houses August 15 to 30 ; 

vines removed December 15 to 31. 
Lettuce. — Seed sown November 15 to 30 ; 

plants set in houses December 15 to 

31 ; crop harvested March 15 to 31. 
Cucumbers. — Seed sown February 1 to 

15 ; plants set in houses April 1 to 15 ; 

vines removed July 1 to 15. 

Plan 2 

Tomatoes. — Seed sown October 25 to No- 
vember 10 ; plants set in houses about 
January 10; vines removed July 1 to 
August 1. 

Tomatoes. — Seed sown June 15 to July 
1 ; plants set in houses August 1 to 
15; vines removed December 15 to 
January 1. 

Plan 3 

Tomatoes. — Seed sown December 15 to 
January 1 ; plants set in houses Febru- 
ary 1 to 15 ; vines removed July 1 to 15. 

Chrysanthemums. — Plants set in houses 
July 1 to 15 ; plants removed December 
15 to January 1. 

Plan 4 

Tomatoes. — Seed sown December 15 to 
January 1 ; plants set in houses Febru- 
ary 1 to 15 ; vines removed July 1 to 15. 


Tomatoes. — Seed sown June 15 to July 
1 ; plants set in houses August 1 to 15 ; 
vines removed December 1 to 15. 

Radishes. — Seed sown December 1 to 15; 
plants removed February 1 to 15. 

Plan 5 

Lettuce. — Seed sown August 1 to 15; 
plants set in houses September 1 to 
15 ; crop harvested November 15 to 30. 

Lettuce. — Seed sown October 15 to 30; 
plants set in houses November 15 to 
30 ; crop harvested February 1 to 28. 

Tomatoes. — Seed sown January 1 to 15; 
plants set in houses March 1 to 15; 
vines removed July 15 to August 1. 

In plan 5, fall tomatoes sometimes 
replace the early crop of lettuce. 
Since tomato plants during early 
stages of growth do not fully oc- 
cupy the space between the rows, 
quick-maturing crops such as rad- 
ishes, lettuce, and beets for greens 
are sometimes planted between the 
rows. These are removed before 
the tomatoes require the space. 
Conditions best suited for the de- 
velopment of the tomatoes should be 
maintained, even though these con- 
ditions are not ideal for the inter- 
planted companion crop. Proceeds 
from a companion crop often cover 
much of the cost of growing the to- 
mato crop. However, many grow- 
ers omit the companion crops and 
simply grow a spring and a fall 
crop of tomatoes as suggested in 
plan 2. This is the prevalent crop- 
ping plan used in Ohio. 


Although greenhouse tomatoes 
grow well in many types of soils, 
loams to silt loams are favored over 
heavier or lighter soils. More labor 
is required in preparing and main- 
taining the heavy clay soils. These 
soils hold the soil water too tena- 
ciously; thus, they tend to remain 
soggy or waterlogged and lack aera- 
tion. Sandy and gravelly soils are 
easily prepared but do not hold 
moisture and mineral fertilizing 

elements so well as heavier soils. 
The silt loams retain moisture w 7 ell, 
yet water drains through them suffi- 
ciently, so there is good aeration. 

Where the soil enclosed by the 
greenhouse is not suited to good 
plant growth or soil is needed for 
raised benches, an excellent soil may 
be prepared by composting fresh 
sod. Well-rotted manure equiva- 
lent to one-fourth the volume of the 
sod should be added. When ma- 
nure is not available, muck, peat, or 
other organic material may be used 
to replace part or all the manure 
in composting greenhouse soil. The 
mixture of manure with muck 
usually gives better results than are 
obtained from the use of all muck 
or other materials. In the compost- 
ing process where no manure is 
used, adequate quantities of a high- 
nitrogen chemical fertilizer should 
be mixed through the compost pile. 

Manure or any of the above com- 
posted materials may also be used 
in houses where the soil is not 
changed. These materials lighten 
heavy soils and add organic matter 
and plant nutrients. When follow- 
ing such rotations as those sug- 
gested on page 4, organic matter 
and much of the nitrogenous ferti- 
lizer are applied before the other 
crops are planted. If composted 
material and nitrogen are added to 
the soil just before tomato plants 
are set, excessive vine growth and 
less fruit will result. 

Greenhouse operators sometimes 
derive their supply of soil for 
benches and beds from land that 
had previously been sown to a cover 
crop. When the cover crop has ma- 
tured it is skimmed off with some 
soil and composted. After the ma- 
terial is composted, it is moved into 
the greenhouse as needed. 

A slightly acid soil, pH 6.0 to pH 
6.5, is best. If lime must be added 
to correct too much acidity, the 
amounts to be used should be de- 


termined by a careful soil test. 
Ground limestone, if needed, should 
be thoroughly worked into the soil 
during preparation for planting. 

Preparing the Soil for Planting 

Many of the larger greenhouse 
growers use power machinery to 
prepare the ground beds for plant- 
ing because of the size of the opera- 
tion and the prevailing high labor 
costs. Small tractors equipped 
with conventional tillage imple- 
ments are mostly used. 

Although rotary soil pulverizers 
do an excellent job of preparing a 
deep fluffy plant bed in one opera- 
tion, the particles of some soils tend 
to cement together again after the 
plants have been set and the soil 
has been watered several times. 
This causes a shortage of oxygen 
and moisture available to the roots, 
as well as greater difficulty of root 
penetration. As a result many 
roots die, the plants are slowed in 
growth, and fruit yields are often 

This unfavorable physical condi- 
tion of the soil can be improved by 
incorporating an abundance of or- 
ganic material through the green- 
house soil. These organic mate- 
rials are often applied in summer 
just before planting the fall tomato 
crop rather than in the winter pre- 
ceding the spring crop. Heavy 
soils require more organic matter 
than light ones to keep them loose 
and friable. Manure is applied in 
one application at the rate of 1,500 
to 2,000 pounds or even more per 
1,000 square feet. It is now com- 
mon practice to use manure and 
mulches for tomato and cucumber 
crops and manure only for lettuce 
and radishes. 

The ideal mulch should act as a 
ground cover during the growth 
of the tomato crop, then remain in 
the soil long enough to keep it in 
good tilth until the following crop 

is harvested. Wheat straw used 
to be the standard material for 
mulching. Other materials have 
been used — peanut hulls, crushed or 
shredded corncobs, oat straw, chaff, 
and old clover, alfalfa, or soybean 
hay. The mulching material is 
spread over the soil surface between 
the plants at the rate of (> to 8 tons 
per acre or 300 to 400 pounds per 
1,000 square feet. Under usual 
greenhouse conditions straw is de- 
composed quite rapidly by the or- 
ganisms in the soil. These orga- 
nisms draw heavily on the soil ni- 
trogen supply during the process, 
thus robbing the growing tomatoes 
of their nitrogen which must be 
added as needed. 

During decomposition of mulch 
material, readily available nitrogen 
fertilizers should be scattered over 
the material and watered into the 
soil before the plants show injury. 
The mulch prevents growth of 
weeds and hard packing of the soil 
between rows. It also promotes 
more even distribution of moisture 
by keeping the surface of the soil 
damp so the small feeding roots may 
grow and feed in the surface layer 
of soil. 

Some experience and careful 
judgment are required in deter- 
mining safe amounts of mulching 
and nitrogenous materials to be 
worked into the soil. Large 
amounts of "woody" mulching ma- 
terials combined with nitrogen may, 
upon decomposition in the soil, re- 
lease quantities of available nitro- 
gen that are too high for best 
yields. Excessive amounts of avail- 
able nitrogen in the soil cause rank 
growth and may interfere with 
fruit setting. 

Chemical Fertilizers 

In the early years of greenhouse 
vegetable culture little chemical 
fertilizer was used. Animal ma- 
nure was then more plentiful, and 


the growers depended on this 
source to supply the essential min- 
eral elements. This source has be- 
come increasingly inadequate as the 
greenhouse tomato industry has ex- 
panded and the supply of animal 
manure around metropolitan areas 
has dwindled. Therefore the grow- 
ers now must depend more and 
more on chemical fertilizers. They 
strive to provide enough fertilizer 
for their particular conditions so 
there will be a sufficient supply of 
plant nutrients to produce a maxi- 
mum crop without carrying over 
excessive amounts of fertilizer 
from one crop to the next. In 
greenhouses this would lead to 
large excesses in the soil and inter- 
fere with tomato plant growth and 

One recommended schedule of 
fertilization for 1,000 square feet of 
soil bed is 25 to 30 pounds of 20 per- 
cent superphosphate and 20 to 25 
pounds of sulfate of potash or mu- 
riate of potash. These fertilizers 
are broadcast and plowed in with 
the manure and mulch residues. 
The grower should apply nitrogen 
fertilizer only as it is needed by the 
developing tomato plants. Some 
growers tend to use too much nitro- 
gen, causing the plants to grow too 
large and vegetative and causing a 
gradual increase in the residual 
amounts in the soil. This excessive 
carryover from crop to crop may be 
reduced before planting another 
crop of tomatoes by plowing into 
the soil several tons per acre of un- 
decayed cellulose material, such as 
crushed corncobs or weathered saw- 

Sodium nitrate and ammonium 
nitrate are two good sources of sup- 
plemental nitrogen for greenhouse 
tomatoes. Some growers find that 
monoammonium phosphate and 
ammonium sulfate are less favor- 
able sources of nitrogen, because 
ammonia nitrogen tends to produce 
thin-leaved, tender plants in the 

spring crops that wilt easily on sun- 
shiny days following cloudy 
weather. Plants so fertilized are 
also said to be more susceptible to 
injury by fumigation. Nitrate ni- 
trogen, on the other hand, may pro- 
duce thicker and darker green 

Experienced operators learn to 
spot early symptoms of nitrogen de- 
ficiency. This is not entirely satis- 
tory because some reduction in yield 
is likely to result from waiting for 
deficiency symptoms. One helpful 
procedure is to have a soil test made 
in advance of planting by someone 
with sufficient experience to inter- 
pret the results correctly. In this 
way more definite information con- 
cerning the fertilizer requirements 
of a particular soil is obtained be- 
fore planting the crop. Many State 
experiment stations provide such 
soil-testing service for residents of 
the State. 

Some greenhouse tomato grow- 
ers are now having chemical tests 
made of tomato leaf tissue to de- 
termine the fertilizer needs of the 
plants during the development of 
the crop. Many growers prefer to 
follow a schedule. The first appli- 
cation of nitrogen is made as soon 
as 3 fruit clusters have set on the 
plants. The number of supplemen- 
tal feedings of nitrogen fertilizer 
w T ill depend on the nature and 
amount of organic matter in the 
soil. Usually 2 to 3 applications 
of 6 to 7 pounds sodium nitrate or 
3.5 pounds ammonium nitrate per 
1,000 square feet of bed soil are 
made to the spring crop. For the 
fall crop usually 1 application is 
sufficient. The fertilizer is broad- 
cast between the rows and watered 
in. Other essential elements are 
usually present in the soil in suffi- 
cient amounts. In some soils defi- 
ciencies may occur. Sometimes ap- 
plications of mixtures of minor ele- 
ments are made to avoid this 
possibility. These mixtures usually 

contain borax, manganese sulfate, 
zinc sulfate, and copper sulfate. 
Four ounces each of these com- 
pounds per 1,000 square feet are 
usually sufficient when applied to 
the soil. When applied as a leaf 
spray the total concentration of all 
chemicals in the spray solution 
should be reduced to % percent or 


The culture of hothouse tomatoes 
developed into a thriving industry 
in the British Isles long before it 
became a commercial enterprise in 
the United States. It is not sur- 
prising then that the small-fruited, 
free- setting, English- forcing vari- 
eties were largely used by green- 
house operators in this country 
when they started growing toma- 
toes. Carter's Sunrise, Sterling 
Castle, Comet, and Best of All were 
the most popular sorts in America. 
They are still grown to some extent 
in greenhouses, especially in the 
Eastern States. 

These varieties, together with 
the varieties Potentate and Ailsa 
Craig developed later, have been 
used extensively as parents in 
breeding new American greenhouse 
varieties. The common charac- 
teristic of these European varieties 
is the large number of small 2- to 3- 
ounce fruits produced per cluster. 

Market preferences greatly influ- 
ence the choice of varieties grown 
in different regions. In the East 
the small 3- to 4-ounce red English- 
forcing types are still most popular. 
Indiana and Ohio prefer the larger 
fruited varieties weighing 6 to 8 
ounces. Most Ohio growers prefer 
pink tomatoes, except in the south- 
ern part of the State. On the other 
hand, most of the Indiana green- 
house tomato growers produce red- 
fruited tomatoes; only around 
Terre Haute are pink tomatoes 

#grown in large quantities. The 
north-central region favors red 
medium-small sorts averaging 
about 4 ounces. 


Globe has been the most popular 
pink tomato for many years. It 
has been used in the Midwest, cen- 
tered in the large commercial green- 
houses of Ohio, more than any other 
variety. In 1930 a selection named 
Globe Strain A was introduced in 
Ohio for special greenhouse use. 
The plants have shorter internodes 
and larger leaves than the original 
Globe variety, and the fruits are 
more uniformly globular and 

Globe Strain A was then crossed 
with a red wilt-resistant variety 
and from this cross was developed 
the pink-fruited, fusarium-wilt-re- 
sistant variety called Ohio Wilt Re- 
sistant Globe. These have become 
great favorites in the Ohio section. 
They are high yielding, have good 
size, ship well, and the dark-pink 
color distinguishes the product 
from the green-wrap southern field- 
grown tomatoes. 

The southern Ohio greenhouse 
operators grow the standard red- 
fruited varieties Marglobe and 
Stokesdale more than any other 
varieties. Both varieties are tol- 
erant of fusarium wilt. 

Michigan State Forcing is the 
most widely grown greenhouse 
variety in Michigan. It was de- 
veloped from a cross of Marglobe 
and Ailsa Craig. The red fruits 
are globe shaped, firm, and average 
4 ounces. The variety is mod- 
erately resistant to fusarium wilt 
but is very susceptible to leaf mold. 

Spartan Hybrid is the first hand- 
pollinated hybrid tomato intro- 
duced for greenhouse culture. It is 
a first-generation cross of Michigan 
State Forcing X Cooper's Special. 
Many greenhouse operators in the 
Grand Rapids area produce their 


own seed. The red fruits are deep 
oblate in shape, not so firm as 
Michigan State Forcing, but tend 
to be more productive in cloudy 
weather. Fruit averages 4 to 5 
ounces. This variety is not now 
grown so extensively as formerly, 
because of lack of firmness in the 

Michigan-Ohio Hybrid, a cross 
of Michigan State Forcing and 
Wilt Resistant Globe, is assuming 
considerable importance in Michi- 
gan. The fruits are firmer and 
more uniform and the plants are 
more productive than Spartan Hy- 
brid when grown during dark 
cloudy weather. 

The English-forcing variety Po- 
tentate is very popular in Minne- 
sota as a greenhouse variety. It is 
productive even in dark cloudy 
weather. The red fruits are firm 
and average 2 to 3 ounces in weight. 

In the New England States and 
parts of New York the English- 
forcing varieties have been largely 
replaced by the varieties Waltham 
Forcing and Improved Bay State. 
Waltham Forcing is the most popu- 
lar variety in this region for the 
spring crop and is used by many 
growers for both spring and fall 
crops. It was developed by selec- 
tion from the variety Best of All. 
The 4-ounce fruits average larger 
than the parent variety and are 
very firm. 

Improved Bay State is resistant 
to several races of leaf mold. The 
red fruits are deep oblate, smooth, 
and average 2y 2 to 4 ounces. It 
closely resembles the English- forc- 
ing type and is used by many Mas- 
sachusetts growers to grow the 
greenhouse fall crop. It sets fruit 
well during dark cloudy autumn 

Waltham Hybrid is a new popu- 
lar forcing variety in the North- 
eastern States. It is a cross of 
Waltham Forcing and Michigan 
State Forcing. The fruits are firm 

and average larger in size than 
Waltham Forcing. 

Several wilt-resistant greenhouse 
forcing varieties have been devel- 
oped in Illinois. These include 
Blair Forcing, Lloyd Forcing, 
Sureset Forcing, Urbana Forcing, 
and Long Calyx Forcing. They are 
all of the larger American-forcing 
type similar to but somewhat 
smaller than Globe, with the excep- 
tion that Lloyd Forcing and Long 
Calyx Forcing are red fruited. 

Another leaf-mold-resistant to- 
mato — Waltham Mold-Proof Forc- 
ing — was introduced by the Wal- 
tham (Mass.) Field Station in 1952. 
It is said to be immune to all pres- 
ently known races of leaf mold. It 
was developed from several crosses 
involving a wild Peruvianum hy- 
brid with Prince Borghese and 
Pan America and Improved Bay 
State. The red fruits weigh 3 to 5 

The Indiana Agricultural Ex- 
periment Station has developed a 
new red-fruited greenhouse va- 
riety called Tippecanoe that pos- 
sesses high resistance to fusarium 
wilt. It is similar to Spartan Hy- 
brid, having resulted from a cross 
between a wilt-resistant Red Cur- 
rant line and Michigan State Forc- 
ing. Tippecanoe is sensitive to 
overfertilization and overwatering 
but is much liked where wilt is 


It is an almost universal practice 
for greenhouse operators to grow 
their own tomato plants. This en- 
ables the grower to start his plants 
at the exact time so they will be at 
the right stage of development 
when he wishes to plant the crop. 
He is assured of a supply of stocky 
plants of the desired age and va- 
riety, and the plants can be trans- 
ferred to the permanent beds with 
the least shock. 


Providing Sufficient Seed and Plants 

An ounce of fresh, well-matured 
tomato seed should contain at least 
8,000 seeds. This should be suf- 
ficient to produce 3,000 to 5,000 
strong, healthy plants. The grower 
should use the best seed obtainable, 
since the total cost of seed is rela- 
tively insignificant as compared 
with the large investment in equip- 
ment and in growing the crop. It 
is good insurance to grow more 
plants than will be needed to set the 
available bed space. 

About 225 plants are required to 
set 1,000 square feet of bed, allow- 
ing between 4 and 4% square feet 
of growing space per plant, which 
is the amount of space commonly 
provided by tomato greenhouse op- 

The plants may be spaced 15 to 
24 inches apart with the rows fur- 
ther apart as the space between 
plants is reduced. As an example, 
plants set 18 inches apart in rows 
3 feet apart have 4i/£ square feet of 
growing room while plants set 15 
inches apart in 3y 2 -ioot rows have 
a little less, about 4y 3 square feet of 
growing space. 

Time for Sowing Seed 

The date for sowing the seed 
should be governed by the desired 
time for the first harvest. About 
4!/2 months should be allowed for 
a fall crop and about 5y 2 months for 
a spring crop. Plants grown in 
summer and early fall develop 
faster than those grown in late-fall 
and early- winter months. Unless 
other crops in a rotation interfere, 
the tendency is to plant the fall crop 
earlier than formerly. Increased 
demands for greenhouse tomatoes 
immediately after the outside crop 
has been killed by frosts and the 
difficulty of obtaining a good set of 
fruit after the prevailing cloudy 
weather that comes in November 
make earlier fall plantings profit- 

able. Moreover, it takes 50 to 60 
days to develop tomatoes from blos- 
soms to full ripeness under late-fall 
and winter conditions, so that if the 
tomato plants are to be removed by 
mid-January, the fruit must be all 
set by mid-November. 

Greenhouse growers vary the 
time of sowing the seed for the 
early-spring crop so as to fit it into 
diverse cropping systems. Since 
the trend is toward a longer tomato 
growing season, the seed is being 
sown earlier than formerly. Con- 
trolled experiments have shown 
that earlier planting not only pro- 
duces the largest yields but also 
usually brings better prices on the 
early-spring market. Some Ohio 
growers with large acreages sow the 
seed for the spring crop as early as 
October 25. These plants are set 
in permanent ground beds about 
January 10 and the harvest begins 
around the first of April. 

Methods Used for Starting the 

Most tomato seedlings for the 
greenhouse crop are started in 
steamed soil mixtures of various 
compositions — one-half composted 
soil and one-half vermiculite ; one- 
half humus or weathered muck and 
one-half fine sand; or a loam soil 
well supplied with organic matter. 

Flats filled with the soil mixture 
for seed germination are usually 
steamed at 10 to 15 pounds' pressure 
for about 3 hours. They are then al- 
lowed to stand, preferably for a 
week or more, before the seed is 

The seed is usually sown in drills 
scant i/^-inch in depth and 2 to 3 
inches apart (fig. 2). A wooden 
lath so notched that it will make a 
drill of proper uniform depth is 
pressed into the screened soil mix- 
ture to make the rows. The seed 
should be distributed uniformly, 4 
to 6 seeds per inch, in the rows. 


Figure 2. — Solving tomato needs in a fiat, a method commonly used for starting 

greenhouse tomatoes. 

which are then filled level full with 
the germinating medium to cover 
the seeds. 

To insure good germination of 
the seed it is important to keep the 
soil around the seed moist until 
after the seeds have sprouted. 
After germination the surface soil 
should be wet no oftener than nec- 
essary to keep the young plants 
growing. Some growers hasten 
germination by setting the seed flats 
over the greenhouse heating mains. 
Temperatures ranging from 70° to 
80° F. are satisfactory during this 
period. After germination is com- 
pleted it is best to reduce the tem- 
perature range to 60° to 70° in order 
to promote stocky growth of the 

Growing the Planting Stock 

Young seedlings should be trans- 
planted as soon as their stems have 
straightened and the seed leaves 

(cotyledons) have opened horizon- 
tally, which is usually 9 to 14 days 
after sowing the seed. The younger 
the seedlings can be transplanted, 
the quicker they recover from the 
shock. When transplanting young 
tomato seedlings, the grower should 
always grasp the plant by one of 
the seed leaves. A little pressure 
on the stems can easily injure the 
seedlings permanently. It should 
also be a routine practice for all 
persons to wash the hands in strong 
soap and water before handling 
young tomato plants to avoid in- 
fecting them with mosaic viruses. 
None of the workers should be al- 
lowed to use tobacco in any form 
while working around the plants. 
After one has smoked or other- 
wise handled tobacco, he should 
always wash his hands again as 
directed above before starting back 
to work. 

One of the most satisfactory 


Figure 3. — Sturdy tomato plants spotted in a deep flat in first bud stage ready for 


methods now used is direct transfer 
of seedlings from the germination 
flat to 4- or 5-inch clay pots where 
they grow until ready to plant. 
Sometimes the seedlings are spotted 
about 4 by 4 inches apart in deep 
flats (fig. 3). Experiments have 
shown, however, that the pot-grown 
plants usually start growing sooner 
and produce ripe fruit 7 to 10 days 
earlier than the plants grown by 
other methods. 

Since the plants for the spring 
crop must be grown during the pe- 
riod of the shortest and cloudiest 
days of the year, it is most impor- 
tant to provide the best possible con- 
ditions for their proper develop- 
ment. The potting soil in which 
the plants are to be grown should 
be a well -aerated sandy loam that 
is high in phosphate and potash but 
is low in nitrate nitrogen. 

High nitrate content of the soil 
with abundant moisture during 
short days will cause the plants to 
grow soft and spindling. Under 
these conditions the first flower buds 

often fail to develop properly and 
produce no good pollen. They 
usually drop oil' and delay fruit set- 
ting for weeks. When grown slowly 
in soil low in available nitrogen 
with moderate soil moisture the 
plants will grow into a fruitful con- 
dition during the winter. In re- 
gions where the smaller English- 
type forcing tomatoes are com- 
monly grown, it is not necessary to 
keep the available nitrogen in the 
soil at such a low level. These va- 
rieties set fruit quite readily even 
when the days are short and there 
is considerable cloudy weather. 
The blossoms of these varieties very 
seldom drop oil' even though not 
pollinated. Where more nitrogen 
can be made available during this 
period the plants develop faster and 
mature more quickly. 

The night temperature should be 
kept as close to 60° F. as is practi- 
cal, with day temperatures main- 
tained between 65° to 70° F. 

In 8 to 10 weeks from seed germi- 
nation these plants should be 8 to 10 


inches tall with strong roots and 
with the first fruit buds partially 
developed (rig. 4). They will be 

Figure 4. — A good tomato plant grown in 
5-inch clay /jot, ready for setting in 
greenhouse bed. 

somewhat deficient in nitrogen as 
indicated by the light yellow-green 
color of leaves and by the purple 
tinge of stems and petioles. The 
plants at this stage should be firm 
but not hard and woody. This is 
the best time to set the plants in the 
ground beds. If they are held 
much longer the root systems will 
become potbound and stunting of 
the plant growth will occur. 

If the plants should become too 
hardened before transplanting, an 
ounce of sodium or ammonium ni- 
trate per gallon of water will stimu- 
late renewed growth. Complete 
all-soluble starter fertilizers are 
now available. These furnish the 
plants better balanced nutrition. A 
good starter solution may be made 
by dissolving 3 pounds of 10-52-17 
fertilizer in 50 gallons of water. A 
half pint of this solution per plant 
is usually ample to stimulate re- 
newed growth of the plants. It is 
best to pour the fertilizer solution 
directly into each pot a day or two 
before the plants are to be trans- 
planted out in the greenhouse beds. 

The starter fertilizer will give the 
plants a quicker start, thus hasten- 
ing the first harvest. 

During the entire plant-growing 
period, the utmost care should be 
exercised to avoid infecting the 
plants with tomato mosaic virus. 
Whenever it is necessary to handle 
the plants in any manner, the 
workers should be instructed to 
wash the hands and contaminated 
clothing and tools with strong laun- 
dry soap and water before touching 
the plants. 

When and How To Set Plants 

About March 1 used to be a favor- 
ite date for setting out the plants 
for the spring crop in the green- 
house. This avoided much of the 
coldest winter weather and thereby 
saved large quantities of fuel. But 
development of modern greenhouses 
has enabled operators to plant at 
earlier dates so the harvest season 
can begin 6 weeks earlier, thus ex- 
tending the harvesting season for a 
longer period. Some growers set 
the spring crop regularly about 
January 10; harvest begins around 
April 1 and closes from July 1 to 
August 15. 

Houses should be warmed thor- 
oughly before the plants are set dur- 
ing winter weather. In order to in- 
sure prompt growth of plants some 
growers introduce steam into the 
tile used for steaming the soil for 
a short time until the soil tempera- 
ture is raised to 70° F. Many grow- 
ers are now giving their soils a com- 
plete steaming before each tomato 
crop and setting the plants as soon 
as the soil temperature has dropped 
to 70° to 80°. Tomatoes should 
never be planted until the soil has 
cooled to 80° or lower. 

Warmed water is also used some- 
times at transplanting time to help 
the plants to a quicker start. A 
word of caution should be added 
here. If soft vegetative plants have 


to be used for winter planting, 
starter fertilizers and extra heat 
should be omitted. 

When plants are grown in sum- 
mer for early-fall planting the days 
are long and usually bright. These 
conditions encourage high carbohy- 
drate (sugar, starch, and cellulose) 
production, and hence the plants use 
larger amounts of nitrogen during 
summer. The plants tend to become 
nitrogen starved, so more nitrates 
must be supplied to maintain good 

On the other hand, when the 
plants are being grown in the short 
days and prevailing poor light of 
winter, much smaller amounts of 
carbohydrates are produced. In 
order to obtain normal growth and 
fruiting of tomato plants there must 
be maintained a proportional bal- 
ance between the amount of nitro- 
gen available to the tomato plants 
and the rate of carbohydrate manu- 
factured in these plants. There- 
fore, during the months of limited 
carbohydrate production, available 
nitrates must be kept low until after 
some fruit clusters have set on the 

To be successful a tomato grower 
must learn to recognize this growth 
relationship and to know what to 
do to keep the carbohydrate-nitro- 
gen ratio in proper proportion. 

After fertilizers and organic sup- 
plements have been plowed under 
and the steaming is done, the soil 
should be given a final surface work- 
ing just before the plants are set. 
This cultivation provides soil aera- 
tion, which stimulates reinoculation 
of the soil-nitrifying organisms and 
reduces the chances of steaming 

The beds are usually laid off with 
a marker or with a line. In large 
houses furrows about 6 inches deep 
are often made with a light tractor. 
The sequence of planting operations 
is varied according to the grower's 
plans. Many growers set the plants 

directly in place, but when the soil 
is to be covered with a mulch it is 
sometimes spread evenly over the 
beds before setting the plants. The 
pot-grown plants may then be set 
in place on top of the mulch and 
left a week or two longer to reach 
the right bud stage before setting 
in the ground bed. 

It is very important, except when 
growing free-setting forcing varie- 
ties, to have the first bud cluster at 
the proper stage of development be- 
fore planting so the blossoms will 
open normally and set fruit. The 
grower must not allow the plants to 
take root in the soil beneath them 
while they are sitting on the mulch. 
If the roots are allowed to penetrate 
into the bed soil the nitrogen and 
moisture available very probably 
will cause the plants to become suc- 
culent and vegetative, leading to 
failure to develop normal blossoms. 

Most growers water the potted 
plants thoroughly the day before 
they are to be planted in the perma- 
nent beds. The plants are then 
easily removed without disturbing 
the rootlets in the soil by inverting 
the plant and jarring it out of the 
pot. The plants are set in holes 
dug deep enough in the bed so that 
the soil from the pot is covered with 
an inch or more of soil when the 
hole is filled. After all plants have 
been set the mulching material 
should be leveled around the plants 
and the plants should be watered. 
Only enough water should be used 
to settle the moist soil around the 
roots and to provide sufficient water 
for good growth — about a quart per 

Growers should always remember 
that tomato plants are to be han- 
dled as little as possible throughout 
their development to avoid so far 
as possible the spreading of virus 
diseases through the plants. When 
they must be handled, the operator's 
hands, clothing, and tools should be 
washed free of any possible virus 


contamination before touching any 
tomato plants. Also, the operator 
should not smoke while in the 


Too much water may ruin the 
crop when the plants are first set 
out. Later in the season when the 
plants have matured and are laden 
with growing fruit much more 
water is required by each plant, so 
overwatering is quite unlikely. Too 
much soil moisture in January and 
February during cloudy periods 
tends to promote vegetative growth 
at the expense of fruitfulness. 
Many growers water with hose for 
4 to 6 weeks after setting the plants 
or until after the first clusters of 
fruit have begun to enlarge, taking 
care to wet the soil just down to the 
root zone. Until after the second or 
third fruit clusters have set, some 
growers prefer to water the spring 
crop only where plants show signs 
of wilting. Sometimes the spring 
crop will grow for 6 weeks or 
longer with only spot watering be- 
fore a general watering becomes 

The frequency of watering dur- 
ing this period will depend mainly 
upon the amount of sunlight and 
the structure of the soil. As the 
season advances the lengthening 
days and more intense sunlight pro- 
mote more normal flowers with 
abundant pollen and faster fruit 
development. By midseason water- 
ing is done about once or twice a 
week and 1 to 1% acre-inches equiv- 
alent of water is applied each time 
in order to satisfy the needs of the 

In the larger greenhouses when 
the water requirements of the crop 
become large, the water is applied 
through overhead irrigation pipes, 
longitudinal sprinkling pipes with 
nozzles that throw horizontal 

streams of water close to the soil, 
or through subirrigation tile. 
Growers prefer to do most of the 
required watering early in the day. 
Operators should use a soil auger or 
spade frequently to check the mois- 
ture content of the soil. They 
should learn to know the moisture 
content of their particular soil by 
its appearance and by squeezing it 
in the hand. 


The regulation of greenhouse 
temperature is second only in im- 
portance to providing the optimum 
amounts of water for the plants. 
While the crop is growing the tem- 
perature should be held between 60° 
to 65° F. during the night and be- 
tween 70° to 75° during the day if 
the sun is shining. The tempera- 
ture may at times range as high as 
80° on clear days without adversely 
affecting the development of the 
crop. On cloudy days the tem- 
perature should be kept around 65° 
to 68°. When this temperature 
schedule is maintained, the fruit 
buds should develop normally and 
the fruits should be smooth and of 
high quality. In no case should the 
night temperature be held below 
58° during fruit bud development, 
as this may cause poorly formed 
blossoms that usually abort, or if 
they set fruit at all the tomatoes 
will be misshapen and of poor 

Ventilation of the tomato green- 
house is essential in removing ex- 
cess heat and humidity and in 
bringing in fresh supplies of air. 
Heating and ventilation should be 
so regulated as to keep the atmos- 
phere of the house in circulation. 
Moisture constantly evaporating 
from the soil surface and transpir- 
ing from the tomato foliage tends 
to build up humidity. 


Outside air may enter the green- 
house through opened side ventila- 
tors and be warmed as it moves 
through the greenhouse, picking 
up excess moisture and carrying it 
out through the top ventilators. 
This is especially helpful in the 
fall and spring seasons to help con- 
trol leaf mold. 

The relative humidity inside the 
greenhouses should be kept below 90 
percent constantly, in order to keep 
under control the leaf mold disease 
that is so destructive to greenhouse 
tomato plants. If the humidity of 
the house is allowed to go over 90 
percent for 1 day, leaf mold in- 
fections may result. 

No rigid rules can be laid down 
for ventilating. Usually the ven- 
tilators are closed at night during 
cold weather when some heat must 
be kept on in the houses. Even then, 
it may be necessary to "crack" 
(slightly raise) the top ventilators 
to maintain enough exchange of air 
to prevent the humidity from build- 
ing up above 90 percent. 

The most dangerous times are 
during relatively mild weather in 
fall and spring when proper night 
temperature may be maintained 
without any heat in the greenhouse 
by keeping the ventilators closed. 
This is likely to create a combina- 
tion of conditions inside the houses 
that will start an epidemic of leaf 
mold raging through the plants. 
No grower should ever be tempted 
at such times to save the small 
amount of fuel needed to provide a 
little heat and sufficient ventilation 
in the houses. 

Major heat regulation is accom- 
plished by opening and closing the 
valves of the heating lines. Hourly 
adjustments are usually made by 
regulating the ventilators. On 
clear days the direct rays of the sun 
raise the temperature inside glass- 
houses very rapidly when the ven- 
tilators are closed. After sunrise 
w T hen the temperature of the houses 

reaches 70° to 72° F., the ventilators 
should be raised to let in fresh air 
and to allow escape of moisture- 
laden air. It may also be necessary 
to close part or all of the valves 
controlling the flow of heat to keep 
the temperature from rising much 


It is not usually necessary to cul- 
tivate where the soil was steamed 
before the crop was planted, except 
to loosen up the surface soil where 
it has become packed down from 
walking over it. When the soil is 
covered with a mulch, cultivation 
is unnecessary. 

In houses where neither steaming 
nor mulching of the soil is practiced 
some cultivation will have to be 
done. Hand cultivators and hoes 
are satisfactory for small opera- 
tions, but garden tractors designed 
to cultivate between the rows and 
between cross-checked plants are 
best for large greenhouse opera- 
tions. Cultivation should always 
be shallow — just enough to break 
up the surface crust and destroy 
any weeds that may have started to 
grow. The tomato feeding roots, 
close below the soil surface, should 
be disturbed as little as possible. 
Breaking up the surface crust helps 
the irrigation water to soak into the 
soil evenly where it is applied. 


The single-stem system of prun- 
ing and training is almost univer- 
sally used by greenhouse growers, 
although a few operators train the 
plants to two and sometimes three 
stems (fig. 5). The small shoots 
that would develop into lateral 
branches should be removed about 
once a week. These lateral buds 
appear at the point where the leaf 
stem joins the main stem. The 
fruitbud clusters appear on the op- 
posite side of the main stem, usually 


Figure 5.— Tomato plants, supported on slender wood stakes, growing in a small 

greenhouse unit. 

above or below the points where the 
leaves are attached. 

The lateral shoots should be re- 
moved while they are still small and 
can be easily removed without mak- 
ing large wounds. It is best to 
break the shoots off rather than to 

cut them ; viruses are readily spread 
from plant to plant by all pruning 
tools unless sterilized after each 
plant operation. The shoot to be 
removed should be grasped with 
thumb and forefinger and bent over 
sharply to one side, then snapped 


off with a sharp bend and pulled in 
the opposite direction. This re- 
versal of direction of breaking 
stress on the leaf axil shoot becomes 
increasingly important when the 
shoot is large, so as to avoid injur- 
ing the leaf axil or the bark of the 
main stem. This method of remov- 
ing plant parts also helps to prevent 
the spread of diseases, particularly 
mosaic and related virus diseases. 
A few growers are also using a 
square of paper tissue for each 
plant so the operator's ringers do 
not directly contact any part of the 
plant. The tissue is discarded and 
a new square is taken before oper- 
ating on the next plant. 

In all training and pruning the 
grower should remember that all 
organic food for fruit development 
must come from the leaves. To 
yield well, the plants need a maxi- 
mum of functioning leaf surface. 
Some growers provide additional 
leaf surface for each plant by al- 
lowing the axillary shoots that are 
immediately below each blossom 
cluster to grow until they have de- 
veloped their first two leaves. The 
portion above the two leaves is then 

After the lower clusters of fruits 
are approaching maturity it may 
sometimes be desirable to prune off 
part of the lower leaves if they are 
yellowing. This will provide bet- 
ter air circulation and will permit 
better distribution of irrigation 
water. It makes easier harvesting 
of the lower fruit clusters and helps 
in the control of leaf mold. 

Most greenhouse tomato plants 
are supported by stout wires run- 
ning parallel to the soil surface 6 or 
more feet above it. These wires are 
directly over the plants and are at- 
tached to the greenhouse frame. 
The most commonly used support 
for each plant is a strong string or 
sisal twine tied to the wire directly 
above the plant with the other end 
tied loosely around the stem of the 

plant near the ground (fig. 6). 
After allowing the plant to grow 
for some distance above the tie it is 
wound loosely around the string, 
always in the same direction. 
While this is being done, the string 
should be kept under the point of 
leaf attachment to the main stem. 
In this way the leaves will not be 
broken and the plant will be sup- 
ported at the bases of the leaf peti- 
oles and will not slip down the 
string. The tender growing tops 
with developing leaves are left to 
grow free for awhile, as they are 
likely to snap off if wound around 
the string all the way to the top of 
the plant. Sometimes the lower end 
of the string is tied to a coil wire 
anchor or to a peg driven in the soil 
near the base of each plant. When 
the plants are laden with excep- 
tionally heavy yields of fruit it may 
be advisable to support the upper 
portion of such plants with extra 
string attached to the overhead 
wire to prevent breakage of sup- 
porting string and consequent loss 
of productive plants. 

Light stakes may sometimes be 
used to support tomato plants. 
They are pushed into the soil near 
the base of each plant and tied at 
the top to small wires overhead. In 
supporting the plant on the stake, 
the best practice is to tie raffia or 
soft twine tightly around the stake 
2 to 3 inches above a leaf petiole or 
fruit cluster, then loop the raffia 
under the base of petiole or fruit 
cluster, take up most of the slack, 
and tie a square knot. 


Although tomato plants are nor- 
mally self-fertilized when grown in 
fields and gardens, some pollination 
of greenhouse tomatoes is usually 
necessary in order to obtain a good 
yield of fruit. The natural air cur- 
rents outdoors insure sufficient 
movement of tomato flowers to dis- 



lodge the pollen and insure its even 
distribution over the stigmatic sur- 
face. Satisfactory crops of free- 
setting tomato varieties are also 
grown in greenhouses without any 
assistance to natural pollination. 
However, most of the greenhouse 
crops grown in the United States 
require some method of jarring the 
flowers, or of transferring the 
pollen by hand in order to obtain an 
adequate set of fruit. 

Mechanical Methods 

Pollination should commence just 
as soon as the first flowers are fully 
opened and should continue until 
all the fruit the grower desires have 
been set. The operation should be 
done regularly, preferably between 
9 and 3 o'clock each day. Pollina- 
tion is especially important in late 
fall and winter when the days are 

Best yields of high-quality fruit 
are obtained by hand-pollinating 
each flower. This is costly and 
timeconsuming, however, so hand- 

pollinating is impractical on a large 
commercial scale. The most effi- 
cient method of pollinating the first 
flower clusters of the spring crop 
and the late flower clusters of the 
fall crop seems to be the electric 
vibrator, which operates on an ordi- 
nary dry-cell battery. This vi- 
brates a wire loop covered with rub- 
berlike material (fig. 7). The loop 
is moved from contact to contact 
with each cluster as rapidly as the 
operator can do it. Every flower 
is shaken several times and many 
pollen grains contact the stigmatic 
surfaces of the blossoms. 

The general shape, size, and 
smoothness of each tomato fruit is 
largely determined by the thorough- 
ness of pollination. Since a single 
pollen grain is required to fertilize 
each seed, it takes many of them to 
fertilize each fruit. If the seeds are 
all fertilized the tomato will en- 
large uniformly, but if not the fruit 
is likely to be only partially devel- 
oped and to be misshapen. This is 
a common cause of low-grade fruit. 

Tomato fruits usually set without 
much difficulty on the first blossom 

Figure 7. — Pollinating tomato flowers With an electric vibrator. 


clusters of the fall crop and the 
later blossom clusters of the spring 
crop. Under these circumstances 
simpler methods of assisting flower 
fertilization are very satisfactory. 
One method commonly used is to 
have an operator walk between 
plant rows, tapping each overhead 
wire sharply with a stick. The vi- 
brations tend to travel along each 
wire in both directions so the 
flowers of plants in adjoining rows 
are also jarred. Thus, the blossoms 
of all plants are repeatedly shaken 
as the operator taps each wire again 
when he walks through between the 
next two rows of plants. Some 
growers prefer to jar each plant di- 
rectly by tapping it with a rubber- 
covered stick. This method is ef- 
fective, but there is more danger of 
bruising the plants or the growing 

The amount of time necessary to 
develop a tomato from a fertilized 
flower to a ripe fruit varies with 
the season. In winter it usually 
takes about 60 days ; in early spring 
about 55 days; in June 40 to 45 

Sometimes, when it is desirable to 
terminate the harvest of a tomato 
crop at a definite time, the vines 
are topped by the removal of the 
growing tips as soon as the plants 
have set all the fruit that can ma- 
ture within the specified time. This 
allows all the food that will be man- 
ufactured by the plants to be used 
for the development of the fruits 
already growing on the plants. 

Chemical Treatments 

Greenhouse tomato plants grown 
in northern latitudes during the 
season of short days and prevailing 
cloudy weather are sometimes stim- 
ulated to set fruit by applying hor- 
monelike chemicals to the flower 
clusters. None of these chemicals 
should be used as a substitute for 
pollination. They should be used 

only to supplement pollination 
when greenhouse conditions are too 
adverse for pollination alone to be 
effective in setting the fruit. 

The flower clusters should be 
sprayed with the chemical hormone 
only after several of the flowers 
have opened. Investigators have 
observed that treating the immature 
flowers resulted in a poor set of rel- 
atively small-sized fruit. In the 
bud stage of a flower both the pollen 
and the ovules are adversely af- 
fected. When applying the chemi- 
cal, the spray should be directed so 
as to avoid as much as possible 
spraying the immature terminal 
vegetative parts of the plant, which 
tend to develop abnormally when 
thus treated. Hormone treatments 
are most satisfactory when applied 
to the face of the flower. 

Only a few of the many com- 
pounds that are known to stimulate 
fruit setting are satisfactory as 
sprays for commercial use. The 
chemicals that have been most 
widely used to stimulate tomato 
fruit setting successfully are para- 
chlorophenoxyacetic acid, alpha- 
orthochlorophenoxy-propionic acid, 
and indole-butyric acid. They are 
sold under several trade names. 
The recommended dosage for the 
first-mentioned compound is 25 to 
30 parts per million and for the 
others 75 to 100 parts per million. 

The fruits of certain varieties set 
by chemical treatments grow soft 
and do not keep well. Buyers can 
distinguish treated fruits from those 
untreated by the remains of the 
blossom caught under the sepals of 
the treated fruits, and they are apt 
to discriminate against them. The 
very firm smaller fruited varieties, 
as grown in the northeast and north- 
central regions, seem to be less sub- 
ject to softening by treatment with 
hormonelike chemicals, and the 
treated fruits are marketed satis- 



In the greenhouse the control of 
disease is essential to profitable to- 
mato production and requires con- 
stant watchfulness. Because of the 
close spacing and frequent handling 
of the plants, the opportunities for 
the spread of disease-producing 
fungi, bacteria, and viruses are 
somewhat greater than with toma- 
toes in the field. On the other hand, 
soil sterilization and some control 
of temperature and humidity afford 
means of disease prevention and 
control that are not available when 
plants are grown out of doors. 

Diseases such as fusarium wilt, 
vertici Ilium wilt, leaf mold, mosaic, 
and root knot occur so frequently 
that regular practices of sanitation 
are needed to prevent serious losses. 
These measures are of value also in 
reducing losses from diseases such 
as stem rot, botrytis rot, streak, 
spotted wilt, and late blight that 
occur less frequently but occasion- 
ally cause severe damage. Good 
cultural practices will usually pre- 
vent serious losses from nonpara- 
sitic diseases such as blossom-end 
rot and pockets. All these- diseases 
and others that affect tomatoes are 
fully described in Farmers' Bulle- 
tin 1934, Tomato Diseases. 


Tomatoes are subject to the at- 
tacks of various nematodes, or eel- 
worms. These are minute, usually 
eel-shaped organisms not visible to 
the naked eye. Various kinds live 
by the millions in the croplands of 
the United States. Many attack 
plants. They are brought into the 
greenhouse in the soil or with in- 
fected plant roots. 

In this country the roots of the 
tomato plant may be attacked by the 
kinds that live within the roots, such 

3 Prepared by Edna M. Buhrer, asso- 
ciate nematologist, Horticultural Crops 
Research Branch. 

as the root-knot nematodes 4 and 
meadow nematodes ; 5 or by the 
kinds that feed on the plant but do 
not entirely enter the roots, such as 
the spiral nematodes 5 and stubby- 
root nematodes. 5 The root-knot 
nematodes, however, appear to 
cause the most damage. The}^ oc- 
cur in many home gardens in most 
of the States, and in greenhouses 
anywhere. They are often the cause 
of significant losses indoors and 
outdoors in commercial tomato 

Any eel worm damage on tomato 
plants is difficult to recognize, be- 
cause nematodes do not produce 
specific aboveground symptoms. 
Tardy growth, unhealthy appear- 
ance, wilting during the hot part of 
the day or during dry weather, or 
yellowing and stunting of the whole 
plant may indicate the presence of 
large numbers of nematodes on the 
roots. Boots of plants suspected of 
being infected with nematodes 
should be examined. When numer- 
ous, such nematodes as the spiral, 
meadow, or stubby-root nematodes 
may produce stunted, short, or 
sloughed-off roots. 

The root-knot nematodes are the 
easiest to recognize. They induce 
the formation of galls, irregular 
knots, and swellings of the roots. 
On the tomato plant these galls may 
be small and hardly noticeable or 
large and irregular, as shown in 
figure 8. Single females or groups 
of them may be found inside these 
galls. They appear as pear-shaped 
whitish bodies just barely visible to 
the naked eye, measuring only 
about one-thirtieth of an inch in 
diameter. A single root may con- 

4 Meloidogyne spp., formerly called 
Heterodera marioni (Cornu) Goodey, but 
now know to comprise a group of many 

5 Meadow nematodes— Pratylenchus 
spp. ; spiral nem&todes= Helicotylenchus 
spp. and Rotylenchus spp. ; stubby-root 
nematodes =Trichodorus spp. 


Figure 8. — Tomato plant infected iriiJi root-knot nematodes. 

tain several hundred of such fe- 
males, eacli capable of producing 
5*00 eggs or even more within the 
span of 2 to 3 months. During the 
growing season the eggs usually 
hatch in a short time and the eel- 
shaped larvae then make their way 
through the soil and enter new 
roots. There they may grow to ma- 
turity and in time produce eggs. 
At a temperature near 80° F. this 
will take about 25 days, while at 62° 
it takes approximately 87 days; be- 

low 55° the root-knot nematodes 
stop their activity. Even if roots 
of a suitable host plant are not 
available or if conditions are other- 
wise not proper for the develop- 
ment of this group of nematodes, 
there is still danger of carrying the 
disease in the soil for at least 2 

Seedlings and young tomato 
plants suffer much more from 
nematode attacks than older plants. 
It is, therefore, essential to protect 


such plants from invasions. After 
long feeder roots have been devel- 
oped, attacks by nematodes cause 
much less damage. 

Recommendations for Control 

Light sandy soils are preferred by 
nematodes. Heavy soils also may 
be infested, but in these the spread 
is much slower. Eelworm pests 
once established in a soil are difficult 
to eradicate ; therefore, every effort 
should be made to prevent their in- 
troduction and establishment in the 
greenhouse. Unfortunately man 
himself is the most effective dis- 
tributor by transfer of infected root 
crops and seedlings and by unclean 
implements. It is important, there- 
fore, to examine carefully the roots 
of tomato seedlings and trans- 
plants. Discard and destroy plants 
with decaying and diseased roots, 
particularly those that have galls 
and swellings. To produce clean 
tomato seedlings, it is best to grow 
them in steam-sterilized soil, in soil 
treated with a fumigant, in ver- 
miculite, or in peat moss. 

If tomatoes have to be planted in 
soil known to be infested with root- 
knot or other nematode pests, treat- 
ment with steam or with one of the 
newer soil fumigants is strongly 
recommended. Properly done, such 
treatments should result in better 
growth, better stands, and increased 
yields that give returns well above 
the cost. Steam sterilization of the 
soil, as practiced in greenhouses 
equipped with the necessary ap- 
paratus, will serve to control nema- 
tode pests. In the absence of steam 
apparatus, the grower should use 
chemical fumigants applied to the 
soil bef ore the tomatoes are planted. 
All of the soil fumigants, through 
volatilization or chemical reaction, 
give off toxic fumes that diffuse 
through the soil and control the 
nematode pests. An interval of 
time, ranging from 5 to 15 days, 

must elapse between application 
and planting to allow time for the 
chemicals to lose their toxic proper- 
ties and for the fumes to escape into 
the air. 

The fumigants most commonly 
used in greenhouses are mixtures 
containing methyl bromide, chloro- 
bromopropene, or chloropicrin. 
These will control certain other soil 
pests and diseases as well as nema- 
todes. Other soil fumigants more 
specifically used for control of 
nematodes are mixtures containing 
dichloropropene and those contain- 
ing ethylene dibromide. 

All these fumigants, except those 
containing methyl bromide, are 
liquids. They are applied by in- 
jection into the soil at closely spaced 
intervals. For small quantities of 
soil no special apparatus for apply- 
ing the chemicals is required; for 
larger quantities, such as ground 
beds, a hand applicator is advisable, 
to deliver the correct amount of 
chemical per injection. Methyl 
bromide is applied as a gas by re- 
leasing it under a gastight cover. 

Further details of application 
procedures for soil fumigants and 
precautions on their use are best ob- 
tained from manufacturers and dis- 
tributors of the fumigants, from 
State agricultural experiment sta- 
tions, or from the United States 
Department of Agriculture. 


The most common pests of green- 
house tomatoes are the greenhouse 
whitefly, aphids (plant lice), spider 
mites, thrips, the garden centipede, 
and the corn earworm. Others that 
occasionally cause severe damage 
include mealybugs, the tomato pin- 
worm, the tomato russet mite, the 
armyworm, cutworms, the cabbage 
looper, and the greenhouse leaf 
tier. 6 

6 For the scientific names of these in- 
sects see table 2, p. 25. 


Table 2. — Pests of greenhouse tomatoes and the effective organic 


[See text for specific control of each pest and p. 28 for precaution] 



Armyworm (Cirphis unipuncta (Haw.))-- 
Banded greenhouse thrips (Hercinothrips 

femoralis (Reut.)) 

Black cutworm (Agrotis ypsilon (Rott.)) - - 
Cabbage looper (Trichoplusia ni (Hbn.)). 
Citrus mealybug (Pseudococcus citri 


Corn earworm (Heliothis armigera 


Foxglove aphid (Myzus solani (Kltb.)) 

Garden centipede (Scutigerella immacu- 

lata (Newp.)) 

Grape mealybug (Pseudococcus mariti- 

mus (Ehrh.)) 

Greenhouse leaf tier (Phlyctaenia rubi- 

galis (Guen.)) 

Greenhouse whiten 1 y (Trialeurodes vapor- 

ariorum (Westw.)) 

Green peach aphid (Myzus persicae 


Onion thrips (Thrips tabaci Lind.) 

Potato aphid (Macrosiphum solanifolii 

(Ashm.)) - ----- 

Tomato pinworm (Keiferia ly coper sicella 


Tomato russet mite (Vasates ly coper sici 


Two-spotted spider mite (Tetranychus 

bimaculatus (Harvey)) 









































For control of pests on tomatoes 
in commercial greenhouses, the new 
aerosol treatments have almost en- 
tirely replaced the older treat- 
ments, such as fumigating with cal- 
cium cyanide or with nicotine on 
steam pipes or in combustible pow- 
ders, or spraying with rotenone, 
arsenicals, or thiocyanates. 

Aerosols are available commer- 
cially and are accompanied with 
full directions for use in the green- 
house and with precautions for pro- 
tection of the operator. The 10- 
percent parathion aerosol is the one 
most widely used on tomatoes. Two 
or three applications on the young 
plants in the pots and another as the 
first blossom clusters form usually 
control all insects and related pests 

until the crop is harvested. Other 
aerosols that are effective against 
certain pests include 5-percent 
DDT, 5-percent TEPP, 5-percent 
sulfotepp, and 10-percent mala- 
thion (table 2). 

All these aerosols are applied in 
the air above the plants at the rate 
of 1 pound per 50,000 cubic feet. 
The applicators usually deliver the 
material at a rate to treat 1,000 
cubic feet in 4 seconds. The foliage 
should be dry, and the greenhouse 
temperature should be held between 
70° and 85° F. The ventilators 
should be closed for at least 2 hours 
after application, or overnight if 
feasible, and then opened for 
thorough ventilation before anyone 
is allowed to work in the house. 


Greenhouse Whitefly 

When whiteflies are present, they 
fly about like snowflakes when the 
foliage is disturbed. They are tri- 
angular in shape. The immature 
insects resemble small scales at- 
tached to the leaves. Heavy infes- 
tations cause yellowing of foliage 
and excessive deposits of sticky 
honeydew on fruits and foliage. A 
black fungus often grows on the 

TEPP and sulfotepp aerosols 
will kill the adults but not the early 
stages of the fly. Applications 
must be repeated 4 or 5 times at 
5-day intervals. Two applications 
of malathion or parathion 2 weeks 
apart will keep this pest in check, 
as residues of these materials kill 
many adults emerging from im- 
mature whiteflies. 


At least three kinds of aphids at- 
tack greenhouse tomatoes. The 
foxglove aphid, recognized by its 
shining pale-green body with two 
dark-green areas on the abdomen, 
causes yellow spotting and distor- 
tion of tomato leaves. The potato 
aphid, a frosty pink or green spe- 
cies, feeds on the young tips and 
blossom clusters. The green peach 
aphid, a small, greasy-green species, 
feeds on the underside of the leaves. 
In addition to their feeding injury 
the aphids may transmit mosaic 

A single application of an aerosol 
containing TEPP, sulfotepp, mala- 
thion, or parathion is effective 
against aphids. 

Two-Spotted Spider Mite 

The two-spotted spider mite, also 
known as the red spider, varies in 
color from pale yellow to red with 
two dark spots. The microscopic 
mites remove the cell contents of 
green leaves, giving them a stippled 
or bronzed appearance and stunt- 

ing their growth. Severe injury is 
accompanied by webbing of foliage. 
Spring crops of tomatoes are usu- 
ally more severely infested when 
preceded by a fall crop in the same 

TEPP, sulfotepp, and malathion 
are effective against spider mites, 
but parathion aerosol is the most 
widely used remedy in commercial 
greenhouses. Two applications at 
10- to 14-day intervals, as directed, 
are necessary to control an estab- 
lished infestation. 


The onion thrips, a small, light- 
brown, slender insect, enters the 
greenhouse during the outdoor 
growing season. Leaves upon 
which this thrips feeds show white 
stippled areas, and when extensively 
injured they turn brown and die. 
This thrips may also transmit the 
spotted wilt virus from dahlia or 
other host to tomato. 

The banded greenhouse thrips 
does not survive outdoors in the 
Northern States. It is usually 
brought into vegetable greenhouses 
on house plants or other ornamen- 

DDT, parathion, and malathion 
aerosols are very toxic to thrips. 
Usually 2 or 3 applications at 10- 
day intervals are required. A 3- 
percent DDT dust is also effective. 

Garden Centipede 

Garden centipedes are present in 
most greenhouses. The milky- 
white creatures, about % inch long 
with 12 pairs of legs, quickly dis- 
appear after they are exposed by 
turning over the soil. In loose soil 
high in organic matter they become 
abundant and destroy the young 
roots and stunt newly set plants. 

If the soil is kept moist to induce 
the centipedes to congregate near 
the surface, large numbers can be 
destroyed by steam-sterilizing the 


soil. Survivors below the zone of 
sterilization or centipedes coming 
from out of doors may make an- 
other treatment necessary during 
the cropping season. Apply a 
lindane spray to the soil between the 
plants and water it in. The dosage 
recommended is 5 ounces of a 25- 
percent wettable powder in 50 gal- 
lons of water per 1,000 square feet 
of bed surface. Equivalent 
amounts of lindane may be applied 
in less water as sprays or in dusts, 
but they should be washed into the 
soil by watering. For newly set 
plants use 1 ounce to 10 gallons and 
pour 1 pint of the suspension 
around the base of each plant. Do 
not use lindane for this purpose ex- 
cept in the greenhouse. 

Corn Earworm 

Corn earworm moths often enter 
the greenhouses in the fall. The 
pale-green or brown-striped larvae 
feed on the tomato fruits, entering 
through holes either near the stem 
or on the side. Decay and shrivel- 
ing of the fruit often follow the 
insect damage. 

Hand picking of infested fruits is 
usually sufficient to check a light in- 
festation. When an infestation is 
severe, dust the plants lightly with 
3-percent DDT to destroy the lar- 
vae while on the foliage. 


Localized infestations of citrus or 
grape mealybugs frequently become 
serious on tomato. They can usu- 
ally be traced to infested ornamen- 
tal plants brought into the green- 
house for the winter. They are 
recognized by the cottony masses on 
the stems and leaves and by the 
black sooty mold with which they 
are associated. 

When the infestation is confined 
to a few plants, remove and destroy 
the plants, rather than resort to con- 
trol measures. TEPP, sulfotepp, 

parathion, or malathion in aerosols 
applied 2 or 3 times at 10-day inter- 
vals will usually destroy a larger 

Tomato Pinworm 

The tomato pinworm occasion- 
ally becomes established in northern 
greenhouses. The grayish-purple 
larvae, about one-fourth inch long, 
bore in the stems, mine the leaves, 
and tunnel in the fruits, especially 
near the stems. Pinworms origi- 
nating from these greenhouse infes- 
tations may persist during the sum- 
mer on potato, eggplant, and horse- 
nettle in the field, and return to the 
fall crop of tomatoes in the green- 
houses. This insect does not sur- 
vive outdoors in the North. 

Omitting the fall crop of toma- 
toes will control the infestation. 
Parathion aerosol and 3-percent 
DDT dust applied at 2-week inter- 
vals are effective remedies. 

Tomato Russet Mite 

The microscopic tomato russet 
mite, an outdoor pest in the warmer 
sections of the country, occasionally 
becomes established on tomatoes in 
northern greenhouses through pur- 
chases of infested plants. The 
mites feed on both surfaces of the 
leaves and on stems. As they in- 
crease rapidly, the leaves become 
papery and the plants may die. 

The mites may be controlled with 
sulfur dust or parathion aerosol, ap- 
plied twice 2 weeks apart. 


Armyworm moths enter the 
greenhouses in the fall, and the 
brown-striped larvae feed on foli- 
age and chew out large areas in the 
side of fruits. 

Malathion and parathion aerosols 
and a 3-percent DDT dust are toxic 
to the larvae and one of these should 
be applied whenever the larvae are 



Dull-black caterpillars hatch 
from eggs laid by moths migrating 
from out of doors. They cut off 
newly set plants at night and hide 
in the soil by day. 

Apply a 10-percent DDT or toxa- 
phene dust over the bed surface at 
the rate of 20 pounds per acre, or 
y 2 pound per 1,000 square feet. Do 
not disturb the soil for several days 
after treatment, to allow time for 
cutworms to contact the insecticide. 
Parathion aerosols destroy cut- 
worm larvae much as they do army- 
worm larvae. 

Cabbage Loopers 

Cabbage looper moths enter the 
greenhouses late in the fall, and the 
pale-green larvae hatching from 
their eggs feed voraciously on the 

Prompt control measures are es- 
sential. Parathion aerosol and 
DDT dust and aerosol are toxic to 
cabbage loopers. 

Greenhouse Leaf Tier 

Slender green larvae occasionally 
attack tomatoes by tying the leaves 
together and feeding on the under- 
side. They are the young of the 
triangular brown moths of the 
greenhouse leaf tier. Infestations 
of leaf tiers in tomato houses are 
usually traced to other crops, such 
as chrysanthemums or snapdragons, 
that accompany or precede the to- 
mato crop. 

Two applications 10 days apart 
of parathion or DDT aerosol or 3- 
percent DDT dust destroy these 

Control Measures for Small 

In greenhouses too small for 
proper application of aerosols the 
following treatments are recom- 
mended : 

A spray containing 2 teaspoon- 
fuls of 40-percent nicotine sulfate 
and % teaspoonful of a household 
detergent per gallon will control 
aphids and mealybugs. A spray 
containing rotenone is effective 
against whiteflies and thrips, and 
fairly effective against spider mites. 

A 3 -per cent DDT dust or a spray 
containing 2 level tablespoonf uls of 
50-percent wettable DDT powder 
per gallon is effective against thrips, 
greenhouse leaf tiers, armyworms, 
corn earworms, and tomato pin- 
worms. Light dusting with sulfur 
will destroy the tomato russet mite. 

Combustible powders or smokes 
containing nicotine for aphids and 
other suitable toxicants for white- 
flies and spider mites may be pro- 
cured in various-sized units for use 
in small greenhouses. 

Hand picking of larvae of corn 
earworms, armyworms, cutworms, 
and leaf tiers is practicable and ef- 
fective in small greenhouses. 


Most of the pests that attack 
greenhouse tomatoes move into the 
greenhouse in the fall from favored 
hosts among nearby field crops, 
weeds, or ornamental plants. It is 
therefore important to avoid grow- 
ing susceptible crops near the green- 
house. Destroy weeds and other 
plants growing near the greenhouse. 
In late summer or fall clean out all 
plant debris and fumigate the house 
with parathion aerosol or sulfur. 
If possible, sterilize the soil with 
steam or methyl bromide. Such 
practices of sanitation will greatly 
reduce the need for pesticides on the 
growing crop. 


To avoid excessive residues on 
tomato plants and fruits, use all 
insecticides at the recommended 
application rates. To avoid plant 
injury, stunting, or abnormal 


growth, use preparations contain- 
ing highly refined toxicants. 
This is especially important in 
the use of DDT and lindane. 
Aerosols containing parathion, 
TEPP, sulfotepp, and malathion 
are extremely toxic, and should 
be used only by a trained opera- 
tor, who will asume full responsi- 
bility and enforce the precautions 
prescribed by the manufacturers. 
The operator should wear protec- 
tive clothing, gloves, and a full- 
face gas mask with an approved 
canister and should wash with 
soap and water after working 
with aerosols. 

Do not use malathion on toma- 
toes within 10 days before har- 
vest or sulfotepp or parathion 
within 15 days before harvest. 
Do not apply TEPP aerosol to 
tomato plants before the first 
flower clusters form, as younger 
plants may be injured by this 


When greenhouse tomatoes are 
grown for local market they are 
usually harvested as they approach 
full-ripe color and are still firm. 
The major part of the greenhouse 
crop is marketed locally and in 
nearby cities and towns. In those 
cases where tomatoes must be 
shipped to more distant markets, 
it sometimes may be necessary to 
pick the fruits at the "breaker" 
stage of maturity — when the first 
spot of pink becomes visible. Such 
fruits will not have quite the same 
high quality that they would have 
attained had they been left on the 
vines until firm ripe. 

Growers should carefully adjust 
time of harvesting tomatoes accord- 
ing to the length of time it will take 
to place the fruit on the market 
after it is picked. The nearer to- 
matoes approach full ripeness on 
the vines the heavier and more 

flavorful they will become. There- 
fore they should always be picked 
as close to firm ripeness as market- 
ing circumstances will permit. 

Usually fruits are harvested 2 to 
3 times a week. During warm 
weather the best time of the day to 
harvest is during the early morn- 
ing so the fruit will be cool when 
it reaches the packing room. 

Practically all greenhouse-grown 
tomatoes are clipped or broken from 
the vines with green sepals at- 
tached, and this distinguishes them 
from field-grown tomatoes. Very 
few greenhouse tomatoes are mar- 
keted with the stems removed as is 
the common practice when harvest- 
ing field-grown tomatoes. Most of 
the stems are clipped close to the 
green sepals with small shears or 
fruit clippers such as are used in 
harvesting citrus fruits. The clip- 
per blades should be short and 
rounded at the tips so the tomatoes 
will not be punctured. Each fruit 
is held with one hand while its stem 
is being clipped off close to the 
calyx. It is desirable to leave no 
protruding stems to puncture ad- 
jacent tomatoes, especially when 
harvesting and packing the larger 
fruited varieties such as are grown 
in Ohio. In regions where the 
small forcing varieties are grown it 
is the common practice to harvest 
greenhouse tomatoes by breaking 
the fruit stem at the joint beyond 
the green sepals. Although this 
method leaves a short stem on each 
fruit protruding from the calyx, 
the growers experience little or no 
damage to these firm lighter weight 
tomatoes due to stem punctures. 

In large establishments hand 
trucks are used to transport the 
baskets of picked fruit to the pack- 
ing room. The tomatoes are sorted, 
graded, and packed according to 
size, quality, and market demand. 
On the market the well-colored 
fruits with stems and green sepals 
attached distinguish greenhouse- 


grown tomatoes from those that are 
field grown. The "green- wrap" 
tomatoes shipped from southern 
fields have all stems removed before 
they are packed for shipment. 

On the markets greenhouse to- 
matoes are judged somewhat by the 
freshness and greenness of their 
sepals, as this is an index to the 
length of time the fruits have been 
removed from the vines. Fresh 
sepals on full-ripe fruits indicate 
that they were recently harvested 
when practically ripe. Tomatoes 
with stems attached lose moisture 
more slowly and will keep fresh for 
a longer time than those with stems 

Various types of packages are 
used for marketing hothouse toma- 
toes. A commonly used package is 
a veneer basket holding 10 pounds 
of fruit. Some growers market 
their tomatoes in square splint bas- 
kets holding 16 pounds. This is a 
convenient size for handling but is 
not so large that the tomatoes are 
likely to become bruised in the bot- 
tom of the basket when marketed 
locally. Fiberboard boxes are re- 
placing wooden containers in many 
places. Hothouse tomatoes pro- 
duced in the North Central States 
are now commonly packed in 8- 
quart fiberboard baskets with over 
handles similar to the basket of that 
size illustrated in figure i). Some 
markets, such as Indianapolis, now 

Figure 9. — A fiberboard basket now 
popular for marketing greenhouse 


pack 8 pounds of greenhouse toma- 
toes per basket ; other markets use 
10-pound baskets. 

In the Northeast most of the 
greenhouse tomatoes going to Bos- 
ton are packed in a 15 -pound fiber- 
board carton that is gradually elim- 
inating the bushel box. It is 12 
inches wide, Hi 14 inches long, and 
4!/2 inches deep. 

For distant shipments regardless 
of the type of package used, each 
tomato should be wrapped sepa- 
rately before packing in shipping 
container and padded liners shou 1 
be provided on the bottom and c. 
the top of the shipping box to af 
ford protection against bruising in 

Some types of containers such as 
splint baskets that are used in mar- 
keting hothouse tomatoes are regu- 
lated as to size and shape by the 
Standard Containers Act and must 
conform to its specifications. The 
grower should be sure that the con- 
tainers he is using conform to the 
law and that they are properly 


When tomatoes are sold by grade 
the grower who has produced a 
fancy pack is justly rewarded for 
his extra effort and expense in grow- 
ing and marketing a high quality 
product. The Federal grades for 
greenhouse tomatoes established by 
the United States Department of 
Agriculture serve as a basis for 
their sale and purchase. More com- 
plete information on tomato grade 
and standard container specifica- 
tions may be obtained from the Ag- 
ricultural Marketing Service, U. S. 
Department of Agriculture, Wash- 
ington 25, D. C. Careful harvest- 
ing at the right stage of maturity, 
avoiding bruising or breaking by 
rough handling, and proper grad- 
ing will help insure better prices 
for the crop.