Mid-winter greenhouse tomato production is not generally recommended for
western Oregon. Poor light intensity and high humidity often result in poor fruit set and
quality. Effective lighting and humidity control is not considered to be economical. Heating and other
production and marketing costs, and competition from outdoor production from California,
Arizona and Mexico, and the availability of greenhouse tomatoes from Canada at competitive prices,
make profitable greenhouse production in western Oregon difficult. Greenhouse production in
British Columbia is possible because of their high inputs and the technical level of management
possible in large operations (the trend is to shift to operations of over 2 acres), and the high
quality glass greenhouses being used in the great majority of the operations, and their
strong marketing organization.
Tomato is the most commonly-produced greenhouse vegetable crop.
Although claims by greenhouse promoters are made that 30 or more lb marketable fruit can be
expected per plant (or plant-space) per year, such production is only possible with very high inputs
in quality facilities and optimal cultural practices. Production in western Oregon of 20 to 25 lb/plant space/year would be a more
realistic top yield. A one crop schedule (December to December) is used by some Pacific
northwest growers and is common in British Columbia, Canada. Growers there start their
crop in January and harvest usually from March through November. A two-crop system is
recommended under western Oregon conditions. This would consist of a fall (August to December)
and a spring (January to June) crop. A two crop system is at less risk from crop pests and
allows fruit set and harvest when environmental conditions are best and competition from outdoor
productions is least.
Excellent references on greenhouse vegetable production are:
Greenhouse Vegetable Production Guide for Commercial Growers 1993-1994
Columbia Ministry of Agriculture, Fisheries and Food., 808 Douglas St.
Columbia, Canada V8W 2Z7.
Managing Diseases in Greenhouse Crops by Wm. R. Jarvis, American
3340 Pilot Knob Road, St. Paul MN 55121-2097
A recent advance in greenhouse soilless tomato production is the Closed Insulated Production System (CIPS). Plants are grown in boxes that enclose the
root system. The shoot extends through a seal in the lid. Capillary water movement in the reservoir is plant-driven and fertilizer diffuses from a fertilizer reservoir within a
protected diffusion zone. This technique is still experimental but shows promise for single-cluster tomatoes. It is a concept that should be
examined by those who are interested in controlled-environment tomato
production. For more information, see the
Variety selection is made to fit light intensity, fertility and disease
resistance requirements. Check
variety descriptions for diseases to which the variety is resistant, and the
season to which it is best
adapted. Size, color, lack of cracks and blemishes, shape, flavor, and
productivity are all important factors in variety selection. Most field
varieties do not perform well in the greenhouse environment.
Varieties such as Dombito, Belmondo, Boa, Jumbo, Trend, and Trust are best
adapted to areas west of
the Cascade Mountains and varieties such as Perfecto and Capello to areas east
of the Cascades.
Caruso, which has sparse foliage, is best adapted to fall cropping and may
produce yellow-shouldered fruit under high light intensities. Some varieties may be
too vigorous, and can become too viney under high water and fertilizer programs. Always test a
variety in the season it will be produced before committing to it.
Varieties (in the 6.5-7.5 ounces fruit range) that have been used in the
Pacific Northwest are:
Capello, Cobra, Laura, Trust and Trend (all uniform ripening); Caruso
Dombito and Jumbo (green shoulder). Varieties suggested for trial are:
Carmello, Contento, Largetto and Match (all uniform ripening); also Dombello,
Peto 109, Peto
656, Peto 761 (all green-shoulder). In all these varieties, provision for
fruit set must be made (see
section on "pollination" below).
Parthenocarpic varieties needing little or no mechanical vibration for
pollination: Carpy, Quasar,
Barry (these produce 4.0 to 5.0 ounce fruit) which may be too small for most
Tomatoes for the U.S. market must be of a large size. Many European
varieties are not large
enough. Know your market requirements for fruit color, size and shape, and
the variety fruit
characteristics before selecting the varieties to use. Fruit under 4 ounces
is considered small, 4-6
ounce fruit is marketable, and fruit over 6 ounces (large) is preferred.
COST OF FACILITIES
Depending on the number of units purchased, double polyethylene
greenhouse costs in 1994
would run about $6.00 to $7.00 per square foot. Hydroponic equipment will
cost another $1.50
to $2.00 per square foot. Land cost, site preparation, foundations, concrete
floors, and electric, water and gas service may cost another $3.50 to $4.00 a square foot.
Modern high-gable glass greenhouses and related automated heating/cooling, hydroponic, and carbon dioxide enrichment
equipment such as those built in Arizona in the mid-1990s may run $20.00 or more per square foot.
A number of different materials are used in greenhouse structures and coverings which can result in
a wide range of total
construction cost. This guide does not address greenhouse engineering or
Approximately 25,000 to 35,000 square feet of greenhouse tomato
production is considered to be
the minimum size economic unit. Smaller units are often used for part time
Oregon, total greenhouse vegetable production was just under one acre in 1994.
This is similar
for the state of Washington. A North Carolina publication reports that about
4000 square feet is
considered enough production area to provide greenhouse tomatoes for about
Plants have been commonly grown in well fertilized, well drained soil
(ground- bed production).
This conventional system is now largely replaced by a soilless culture system.
Soilless culture utilizes totally artificial means of providing plants with nutrients and
anchor. Major advantages are the elimination of the need for soil sterilization by steam or
chemicals, and precise control of the application of nutrients and water.
Due to environmental concerns, restrictions may be in place regarding
the disposal of excess
fertilizer solutions and growing media. Possible options are to discard
fertilizer solutions by using
it on pastures or in other agricultural applications, and to recycle growing
media by blending it
with other potting mixes or agricultural soils. Consult appropriate agencies
for available options.
Soilless culture is more demanding and less forgiving of mistakes than
conventional soil culture.
Good nutrient media composition and nutrient balance through the entire crop
Soilless culture methods allow production of tomatoes in areas where
suitable soil is not available
or where disease or other conditions make ground production unfeasible.
Although the system
can be automated to minimize irrigation and fertilization labor input,
continuous monitoring of
most aspects of plant growth and culture media, nutrient balance, and a
of the crop and its physiology is critical. Costs of the automatic devices
and special nutrient
media are substantial.
All other aspects of production remain the same as with conventional
culture. There are little, or
no yield or quality advantages over conventional production if the quality of
management is equal.
Excellent books on this subject are:
Hydroponic Food Production by Howard M. Resh, Woodbridge Press Publishing
Santa Barbara, CA 93160.
A Guide for the Hydroponic & Soilless Culture Grower by J. Benton
Jones, Jr., Timber Press,
POB 1631, Beaverton, OR 97075.
Two major soilless culture systems are used, those in which plant
nutrients are recirculated
(closed-system hydroponics), and those that utilize artificial media for
plants to anchor but new
nutrient solution is constantly provided to the plants and the excess nutrient
solution is not
collected and recirculated (open-system hydroponics or bag culture).
Closed-system hydroponic culture is the growing of plants in troughs
or tubes, where plants are
anchored in gravel, sand, or artificial soilless mixes; or without artificial
media for anchor, such as
nutrient-film technique (NFT). Any system used must be suitably built to
allow proper application
and recirculation of the nutrient media. Flow rates of 1 1/2 to 2 quarts per
minute are most
common. In a closed-system, the nutrient solution is regularly monitored and
adjusted for pH as
needed. Because plants take up nutrients at different rates, and roots exude
imbalances and problems can occur. To prevent undesirable build up of certain
nutrient solution may need to be changed every 2-3 weeks with changes as often
as once per
week during periods of peak growth. By careful monitoring of nutrients in
solution and especially
the electrical conductivity (EC) daily, and by installing activated charcoal
filters to remove certain
toxic root exudates, a large reservoir of nutrient solution may be maintained
for one crop cycle
(up to 10-11 months). The EC should be maintained at 2.5, so that fresh water
is added when EC
exceeds 2.5 and new, complete nutrient solution is added to bring the EC back
Bag Culture uses artificial media (usually rockwool) packaged in 3
or 4-cubic-foot bags.
Rockwool comes in two densities, standard and low density. The low density is
used for one year
and discarded. The standard density may be sterilized and reused for up to
three crops. Two
common trade names are Redi-Earth and Metro-Mix. The 4 cubic foot bags are
tomatoes. Two rows of tomatoes are usually planted per bag with plants spaced
16 inches apart
in each row with rows 16 inches apart. Bags are placed in rows 6 feet apart,
and spaced down the
row to allow a uniform 16 inch spacing between plants. A drip irrigation
system with spaghetti
drippers for each plant is used to distribute the nutrient solution. A
10%-20% excess solution is
applied during cloudy cool periods and 25% to as high as 50% under sunny, warm
provide drainage and prevent salt buildup. This excess should be collected
and discarded or may
be reused with certain restrictions.
Common modifications of this system (to reduce cost) utilize 3-5 gallon
plastic bags or pails with
saw dust, pine bark or rice hull media. Western Hemlock and Douglas-fir are
available and the main ones used in the Pacific Northwest. Avoid western red
cedar because of
possible toxicity from chemicals in it. Use a medium-fine grade of
horticultural grade (guaranteed
to be free of toxic chemicals that may be used by the lumber industry). If
too fine a grade, the
saw dust will limit oxygen exchange as it breaks down resulting in root
suffocation. Prior to using
saw dust, test leachate conductivity for any salt accumulation and leach bags
with fresh water if
needed. Modifications of the fertilizer program are necessary to compensate
for specific media.
Of particular concern is possible manganese toxicity since manganese can
accumulate in wood to
toxic levels. Check the first leaf tissue samples and adjust manganese
applications as needed.
Hydroponic greenhouse promoters have often failed to present their
product fairly and have
created unrealistic expectations. None of the package offers of equipment and
guarantees success. Investigate thoroughly before making financial
Greenhouse tomatoes are always grown from transplants. Use a special
part of the greenhouse to
grow these transplants. This can be a separate greenhouse, or an area divided
off from the main
greenhouse where day and night temperatures can be separately, and accurately
Plant the spring crop in early December, so harvest will begin in
mid-March. For this crop, seed
into flats, then transfer seedlings to 4-inch containers set close together
when the first true leaf has
formed. Space the containers at an 8 x 8 inch spacing two to three weeks
later to finish growing
the transplants. Set plants in their permanent location about mid
Although 3.5 to 4 square feet of space per plant is often
used in other areas, about 4.5 to 5 square feet per plant would be more appropriate under western Oregon
Plants should be trained to a single stem and supported by strings hanging
from overhead wires.
Vines are usually removed by the end of July or early August when outdoor
available locally. From seeding, it takes about 5 months for a spring crop to
begin to fruit.
Plant the fall crop in mid-June, and set the plants in their permanent
location about August 1. It
takes about 3.5 to 4 months from seeding until first pick for a fall crop,
which should begin in
early October, after local tomatoes are no longer available. Aim for a
production peak around
Thanksgiving, terminating after Christmas or when heating costs and lighting
limiting in December.
For more information on this subject, see the file Florida Greenhouse
Accurate temperature, humidity, and carbon dioxide control are
control is accomplished in many ways ranging from totally manual, to
computer-assisted control. Computers are also used to monitor fertilizer and
A major consideration in environmental control is that of providing
temperature and humidity
conducive to active movement of water and nutrients through the plant for
This is done by maintaining a humidity of between 60 and 80% during daylight
hours. In the
Pacific Northwest, light intensity and duration are limiting factors in winter
making the economics
of supplemental lighting an important consideration. Light intensity is
influenced by external
factors such as cloud cover and fog and also the quality of the greenhouse
covering and its
condition. Dirt, dust, condensation and degradation of the covering material
itself can seriously
If a greenhouse is to be kept closed for long periods (several days at a
time) to conserve heat, you
should provide suitable carbon dioxide generating equipment (see below).
irrigation to control increased humidity and control of increased disease
problems also become
critical in houses with reduced ventilation.
Temperature requirements for major greenhouse vegetables differ. In
general, the cooler
temperatures are used when light intensities are low. For tomatoes, days, 70
to 75 F; nights,
minimum 62-65 F. Where day temperatures might exceed 85 to 90 F, cooling
needed to prevent fruit set failure and to allow proper red color developing
in the maturing fruit.
Tomato flowers form about 3-4 weeks before they become visible. The
first flowers form about
the time the seedling cotyledons unfold and the first true leaf is just
visible. Research has shown
that if tomatoes are subjected to a cold treatment at this time, the first
cluster will develop sooner,
there will be less leaves and shorter internodes to the first cluster, the
cluster will have more
flowers and set more and larger fruit. Varieties differ in their response to
cold treatment. Some
varieties may develop rough fruit in the first cluster after exposure to cold
treatment, so always
test the variety you are using before subjecting your whole crop to a cold
treatment. Do not subject the variety 'Trust' to cold treatment for the reason just given.
Cold treatment consists of exposing seedlings at the time of cotyledon
unfolding to continuous
(day and night) temperatures of 52 to 56 F until the plants reach the two true
leaf stage. This may
take ten days to three weeks. Ten days are sufficient in sunny weather while
up to 3 weeks may
be needed during cloudy, winter weather.
Following cold treatment, night temperatures should be raised to 58-62 F
and day temperatures
should be maintained at 60-62 F during cloudy days, while 65-75 F should be
sunny or partly cloudy days.
Carbon dioxide enrichment
Carbon dioxide is normally present in the atmosphere at a concentration
of 300 parts per million (ppm). Carbon dioxide levels in greenhouse air may be depleted to
levels that may limit plant growth, especially in tightly sealed greenhouses and when ventilation is
restricted during daylight hours. Addition of carbon dioxide to greenhouses has been demonstrated to
improve vegetable yields. Concentrations of 1,000 ppm. or more in greenhouse atmospheres have
given the best results. Yield increases of 20% or more have been reported for tomatoes under
certain conditions. Carbon dioxide generating and monitoring equipment is readily
available. Flue gasses from certain types of heaters and fuels, and even liquid carbon dioxide are
used. Investigate the
various models and types before purchasing.
Concentrations should be adjusted for light intensity and growth stage as
Bright, sunny weather 1000 ppm
Cloudy weather 750 ppm
Young plants 700 ppm
During moderate ventilation 350 ppm
Light intensity during seedling growth is directly related to the number
of days to flower and
yield. Low light intensities delay flowering and reduce fruit set and total
yield. Under western
Oregon winter conditions, light levels are not adequate for good commercial
production. This is
due to both the shorter days of winter and to frequent cloud cover and fog.
Based on research
from Canada, winter light conditions in western Oregon can be expected to
result in as much as a
20-day delay in flowering and a 50% reduction in early yield for a crop
intended for late winter
and spring harvest. Supplemental lighting becomes very important during this
period and also
when plant populations are increased (and less than 4.5 to 5.0 square feet per
plant is used).
High intensity discharge (HID) lamps, including high pressure sodium and metal halide lamps,
are the only types that provide sufficient intensity and light quality for supplemental lighting.
Although these may be used to supplement light during the day and/or to extend daylength,
the economics of their use has not been determined. Note: Low pressure sodium lamps, such as
the yellow-orange lights used in street lighting, should not be used due to the adverse effect that their
light quality has on plant growth habit.
Light quality affects plant growth. Most high pressure sodium lights,
designed to produce high
levels of photosynthetically active radiation (PAR), tend to produce
internodes. To compensate for this, metal halide lights that provide a
greater portion of the blue
spectrum may be added. Light placement and lighting schedules also affect
growth and pollination.
Light intensity is a function of lamp wattage and distance from the
plant canopy. About 650 footcandles at the leaf surface is considered the minimum intensity necessary for normal growth
(for rough conversion purposes, multiply micromoles by 7 to get footcandles). With
one design, a 1000-watt metal halide lamp covers approximately 112 square feet when 600 footcandles are desired.
This translates to approximately 32 fixtures needed for a 30' x 120'
greenhouse. Since each 1000-watt fixture gives off about 3750 BTU per hour, fuel savings would also be
realized during the
time the lights were operating. Growers must carefully evaluate supplemental
lighting and test its
efficacy under their conditions. Growers seriously considering supplemental lighting
should also investigate the overall cost using 400-watt bulbs, even though more fixtures would be needed.
Although supplemental lighting increases yield under adverse sunlight
conditions when all other
production conditions (carbon dioxide, etc.) are optimal, the increased cost
operation and maintenance of the lights and price competition from other
tomato production areas
makes the economics of supplemental lighting marginal in Oregon.
Painting all interior surfaces white and using a reflective white plastic ground cover between plant rows helps maximize
light intensity within the greenhouse.
Commercial fertilizer mixes are available through horticultural supply
companies. Tailor fertilizer
programs for specific crops and soil fertility situations. Proper fertility
is necessary for success.
Plants have different fertilizer requirements during different stages of their
Whether you use soil or a soilless system, no single set of recommendations
will apply, so use soil
tests to determine initial applications, and monitor fertility levels by leaf
analysis throughout the
growing season. Both soil tests and leaf analyses are available through
Oregon State University
Conventional soil culture
A routine fertilizer program would be the addition of 0-20-20 fertilizer at
1,000 to 2,000 lb/acre before the fall crop, and 650 to 1,000 lb before the spring crop
or, you can supply
phosphorous by applying 46 percent triple super phosphate at 300 to 500 lb/acre and
potassium by using potassium sulfate at 300 to 400 lb/acre.
Add N as ammonium nitrate, calcium nitrate, or potassium nitrate
before planting and
throughout the season, depending on the amount of organic matter in the soil.
Feed weekly with
solutions of balanced fertilizers.
Proper feeding of tomatoes with N is critical. Too much N
when the plants are small
will result in soft growth, small flower clusters, and poor set. Apply
N in limited quantities
before planting, at about 50 lb/acre, and apply weekly as necessary to
N levels in the leaves. Nitrogen levels may be monitored by regular
Micronutrients are normally provided by the soil's clay and organic
fractions. Soil tests are
necessary to determine which if any micronutrients must be added.
A number of soilless culture systems are available. These are variations
of the "closed" or
"open" systems described earlier. Fertilizer proportioners are used to
accurately inject the proper
amount of nutrient concentrate into the water stream used for irrigating the
Choose a high quality fertilizer injection pump and system to minimize
problems. Follow directions carefully in preparing and dispensing the
nutrient solution. The
major advantage of bag-culture, is the reduced management of nutrient solution
the elimination of nutrient circulation, that is required in "closed"
hydroponic systems. All major
and micro-nutrients must be added, and kept in balance.
Totally soluble hydroponic fertilizer mixtures are available from
regional horticultural supply
houses. Follow manufacturer's recommendations carefully and completely as
for tomatoes. Improper alterations of formulas or instructions for their use,
can result in serious
Most commonly at least two stock tanks are needed to prevent insoluble
forming when the nutrients are mixed and injected. One stock tank is usually
used to mix
potassium nitrate, calcium nitrate and iron chelate. The other contains the
magnesium sulfate, potassium chloride and the rest of the micronutrients.
This is done to prevent
the formation of insoluble precipitates that most commonly occur from the
mixing of calcium
nitrate and phosphorous materials.
The use of more expensive "technical grade" fertilizer salts eliminates
sludges from forming.
Where "fertilizer grade" materials are used, sludges will form in the
potassium nitrate, calcium
nitrate tank due to insoluble additives used in these fertilizers to prevent
caking and dust.
For a check on crop progress leaf samples should be taken at regular
intervals beginning at about
the time the third cluster begins to set. Sample the whole leaf with petiole,
choosing the newest
fully expanded leaf below the last open flower cluster. Sufficiency leaf
analysis ranges for newest
fully-expanded, dried whole leaves are*:
Macronutrients (%) Micronutrients (parts per million)
Before fruiting During fruiting Before fruiting During fruiting
N: 4.0-5.0 3.5-4.0 Fe: 50-200 50-200
P: 0.5-0.8 0.4-0.6 Zn: 25- 60 25- 60
K: 3.5-4.5 2.8-4.0 Mn: 50-125 50-125
Ca: 0.9-1.8 1.0-2.0 Cu: 8- 20 8- 20
Mg: 0.5-0.8 0.4-1.0 B: 35- 60 35- 60
S: 0.4-0.8 0.4-0.8 Mo: 1- 5 1- 5
Toxic levels for B, Mn, and Zn are reported as 150, 500, and 300 ppm,
* Taken from J.M. Gerber 1985. Plant growth and nutrient formulas.
pp.58-69. In A.J. Savage
(ed.). Hydroponics Worldwide: State of the art in soilless crop production.
Int'l Ctr. for Special
Studies, Honolulu, Hawaii).
If mulches are used, apply to the soil when tomatoes are about two feet
high. Straw mulch is most common, used at about 200 bales per acre. The mulch reduces evaporation
of water from the soil and prevents compaction of the surface. White (reflective) plastic
mulches are recommended to control weeds, conserve moisture, reduce humidity, and improve
Maintain an adequate supply of water to plant roots. Excess water
reduces soil aeration. Young
plants put in the greenhouse in mid-winter May need to be watered only once
every 10 to 14 days.
The same plants in mid- summer may need water every two or three days in
ground beds. A fall
crop would need a total of about 15 to 18 inches; a spring crop may need 20 to
25 inches of
With bag culture, mature plants may need to be watered several times a
day. One to 3 quarts per
plant per day may be needed depending on growth stage and plant size.
Tomatoes are self pollinating under open field conditions. Pollen sheds
and fertilization occurs as
a function of normal air movement and its agitation of the plants and flowers.
conditions, flowers need to be agitated mechanically, or fruit needs to be set
using plant chemical
hormones that are sprayed on flower clusters on a regular basis.
A few new varieties have been developed that are parthenocarpic (need no
pollination, and are
seedless). These generally have small to medium size fruit and have not been
tested adequately in
the Pacific Northwest (see section on "varieties" above).
Pollination by mechanical vibration is recommended with the large
fruited U.S. and European
varieties. This is accomplished using a hand operated electric vibrator
available from horticultural
supply companies. These vibrators operate on 110 volt or battery power. The
models use a 6 or 12 volt motorcycle battery. Units using flashlight
batteries have insufficient
action for best pollination. Many other methods have been tried or tested.
None have been as
Timing is important when using mechanical vibrators to set fruit.
Pollen sheds most readily when
temperature is at its peak, and relative humidity lowest on a given day. The
optimum time for that
is between 11 a.m. and 3 p.m. during winter and early spring. Each flower
cluster needs to be
vibrated every day, as long as flowers are still opening in that cluster, to
accomplish pollination of
the flowers that open on that day.
Note: Special bees (bumble bees) are now being used for pollination.
These bees mechanically
agitate tomato flower clusters to acquire pollen and thus accomplish
pollination. Currently, the
high cost of obtaining these bees has limited them to use in very large
ranges. The bees would have to be obtained from special bee keepers.
Chemical fruit set is commonly used in European greenhouse tomato
production on varieties that
have been specifically developed to produce high quality fruit with this
method. Most large
fruited varieties used in the U.S. will develop hollow, soft and misshapen
fruit with the use of
chemical setting agents, therefore chemical fruit setting is not
PRUNING AND TRAINING
Auxiliary branches must be pruned as the plant is trained to a single
stem, supported by string to
an overhead wire. In rare occasions, especially when grafted plants are used,
plants may be
trained in a double stem configuration.
With varieties that tend to produce small fruit, cluster pruning is used
to increase fruit size, and
limit the number of fruit per cluster. Generally, 3-4 fruit per cluster are
allowed to develop with
these varieties, with three fruit per cluster during the fall and winter cloudy weather
and four during the sunny late spring and summer period. Fruit number per cluster is the factor
that most affects fruit size, assuming other growth conditions are adequate.
To reduce the likelihood of disease spread (especially Tobacco Mosaic
Virus), exercise careful
sanitary procedures. Workers should use disposable gloves, disposing them,
pruning instruments at the end of each row. No tobacco products should be
allowed in the
greenhouse, and users of such products must not handle TMV susceptible tomato
NON-PATHOGENIC FRUIT DISORDERS
Blossom-End Rot: Varieties differ in susceptibility. Caused by
calcium imbalance or deficiency
during critical stage of fruit differentiation and expansion, usually induced
by water stress.
Gray-Wall: Linked to high plant vigor, associated with high rates
of nitrogen fertilization with
high soil moisture and low temperature. In some cases certain bacteria, fungi
mosaic virus are thought to be involved in gray wall. Often associated with
blotchy ripening (see
Blotchy Ripening: Promoted by low potassium levels in the fruit,
high soil moisture and
humidity and fluctuating temperatures during fruit ripening (above 85 F.) and
low sunlight levels,
or shaded areas in the plant canopy. Aggravated by compacted soils.
Solar yellowing: This problem occurs most commonly on fruit
ripening in late May and June
when days are longest, sunlight is most intense, and temperatures exceed 85 F.
conditions, lycopene (the red pigment in tomato) fails to develop normally in
leaving only the carotene (yellow) pigment to show at the shoulder or, with
tomatoes, where the dark green portion was. Even with temperatures under 85
F. the surface
temperature of exposed fruit, especially those with dark green shoulders can
become high enough
to inhibit normal red color development. In other parts of the day or night,
when temperatures do
not exceed 85 F, some red color may develop, resulting in an orange, rather
than a yellow
abnormality. To reduce this problem, protect fruit surfaces from short-wave
solar radiation by
altering pruning practice in March and April by allowing two leaves to form on
rather than removing the axillary branches. The use of non-phytotoxic white
wash will also help if
applied when fruit are at the mature green stage. The white wash will have to
be removed before
the fruit is marketed.
Roughness and scars: Varieties differ in susceptibility.
associated with large fruit. Particularly
severe when young plants are exposed to cool temperatures, and night
temperatures below 50 F.
when flower clusters are differentiating.
Fruit cracks: Varieties differ in susceptibility. Promoted by
fluctuations in soil moisture and
temperature. Often seen when varieties developed for hot, arid climates are
subjected to humid,
HARVESTING, HANDLING, AND STORAGE
Yields from a two-crops-per-year system would be about 8 pounds of fruit
per plant from the fall
crop, assuming a 2 to 3 month harvest period ending in late December (0.8
considered very good). Approximately 12-15 pounds of fruit per plant may be
realized from the
spring crop assuming a 4 month harvest period ending just after the July 4th
Yield from a single-crop-per-year system, where harvest begins about mid
October and ends in
July the following year, could produce a total of about 25-27 lb/plant (based
lb/plant/week). The lower output per week per plant shown is due to adverse
conditions (cloudiness and high humidity) generally experienced west of the
Fruit is harvested when mature green if it is to be held before
marketing. Mature green fruit have
well developed internal gel, and may have internal tissues that are beginning
to turn red. Vine ripe
fruit ranges from fruit just turning red to fully ripened, depending on market
harvesting and handling, avoid bruising fruit.
The USDA Grade Standards for Fresh Tomatoes recognize 6 official color
1) Green - surface of the tomato is completely green;
2) Breakers - a definite break in color from green to tannish-yellow,
pink or red on no more than
10% of the surface;
3) Turning- more than 10% but less than 30% of the surface, in the
aggregate, shows change as
in 2) above;
4) Pink- more than 30% but less than 60% of aggregate surface shows
pink or red color;
5) Light Red - more than 60% of aggregate surface is reddish pink or
red provided that not more
than 90 % is red;
6) Red- more tan 90% of surface in the aggregate show red color.
STORAGE (Quoted or modified from USDA Ag. Handbook 66 and other sources)
Store mature-green tomatoes at 55 to 70 F; ripe fruit at 45 to 50 F and
a relative humidity of 90
Mature-green tomatoes cannot be successfully stored at temperatures that
greatly delay ripening.
Tomatoes held for 2 weeks or longer at 55 F may develop abnormal amount of
decay and may fail
to develop a deep red color. The optimum temperatures for ripening
range from 65 to 70 F. Tomatoes will not ripen normally at temperatures above
80 F. A
temperature range of 57 to 61 F is probably most desirable for slowing
increasing decay problems. At these temperatures the more mature fruit within
range will ripen enough to be packaged for retailing in 7 to 14 days.
Fruit held below 50 F become susceptible to alternaria decay during
Increased decay during ripening occurs after 6 days of exposure at 32 or 9 days
at 40 F.
Mature-green tomatoes may also be damaged by low temperatures in the field. A
of tomatoes exposed to temperatures below 50 F for a week before harvest would
develop alternaria rot even at recommended storage temperatures. Some loss
due to chilling can
be expected in fall-grown tomatoes exposed for over 95 hours to temperatures
below 60 F during
the week before harvest. Severity of chilling increases with increases in
exposure time, so 135
hours exposure to below 60 F may result in heavy losses.
Chilling periods for fruit in storage and during transit, have a
cumulative effect. Thus, fruit chilled
for only a short period in storage can become very susceptible to decay when
held for only a short
period at chilling temperature during marketing. Tomatoes should be kept out
of cold, wet rooms
because in addition to potential development of chilling injury, extended
refrigeration damages the
ability of fruit to develop desirable fresh tomato flavor.
Semi-ripe tomatoes with 60 to 90% color can be held up to a week at 50
F. If held longer, they
will probably not have a normal shelf life during retailing. Riper tomatoes
will tolerate lower
temperatures. For example, "firm-ripe" tomatoes can be held a few days at 45
to 50. Long
holding of ripened tomatoes at low temperatures (40 and below) results in loss
of color, shelf life,
When it is necessary to hold fully-ripe tomatoes for the longest
possible time before their
immediate consumption upon removal from storage, as for example, for
ship-board or overseas
use, they can be held at 32 to 35 F. for up to 3 weeks. Such tomatoes,
would not be of high quality and would have little if any shelf life
Fully ripe: When it is necessary to hold fully ripe tomatoes for the
longest possible time before
their immediate consumption upon removal from storage, as for example, for
overseas use, they can be held at 32 to 35 F for up to 3 weeks. Such
acceptable, would not be of high quality and would have little if any shelf
life remaining. Mature-
green, turning, or pink tomatoes should be ripened before storing at such low
A storage temperature of 50 to 55 F is recommended for semi-ripe to
fully ripe greenhouse-grown
tomatoes. Ripening of less mature tomatoes at 70 F is recommended before
storage at 50 to 55
Research showed that an atmosphere with 3% oxygen and 97% nitrogen
extended the life of
mature-green tomatoes up to 6 weeks at 55 F and that the flavor of the ripened
fruit had no
off-flavor and was acceptable to the taste panel. A 1% or lower oxygen level
off-flavor. Increased carbon dioxide levels provide no benefit; in fact,
levels of 3 to 5% have been
reported to cause injury at 55 F.
One function of post-harvest handling in packing houses today is the
washing, brushing and
cleaning of produce to remove any pesticide residues that may be on the fruit.
themselves well to such procedures.
Package tomatoes by size in 8 to10-lb, single layer cartons, or 20-lb
double layers. Use only
containers intended for greenhouse-produced fruit, and so designated. In
general only top grade
fruit is marketed. Greenhouse tomato fruit is usually individually
differentiated with stick-on
labels. Misshapen and defective fruit should be removed from vines as soon as
it is so recognized.
Proper control of plant disease is critical in greenhouse environments,
where high temperatures
and humidity are ideal for diseases to develop. Insect and nematode
infestations, too, can become
rampant under the confined greenhouse conditions.
You can control most fungus and virus diseases with fungicides and proper
sterilization of soils, growth media, and equipment. The most serious fungus
disease on tomatoes
are leaf mold (Cladosporium), early blight (Alternaria), leaf
spot (Septoria), gray mold (Botrytis),
and the wilt diseases (Fusarium and Verticillium).
Tobacco mosaic virus can be serious and several other virus diseases may
sanitation to reduce spread by workers, soil sterilization, and control of
insect vectors are some of
the methods of control.
Early control of white fly, aphid, and spider mite infestation is
important. Several chemicals and a large number of biological controls are
available to control these pests.
Note that Oregon law requires that agricultural pesticide use be reported to the Oregon Dept. of Agriculture
through it on-line PURS system.
Nematodes may become a problem in either soil or hydroponic culture.
Sterilization of soil or
hydroponic media is used as a preventative measure. Current recommendations
on pesticides are
available from your county Extension agent. Always follow label instructions
See also the Greenhouse Plants (Tomato) section in the Oregon Plant Disease Guide.
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