Growing Tomatoes Organically
Selecting Tomato Varieties
Tomato tags have a sequence of capital letters after the
variety name such as VFNTA.
Each letter stands for resistance to a different disease or pest.
V = verticillium wilt, F = Fusarium wilt, N = nematodes,
T = tobacco mosaic virus, A = alternaria stem rot canker.
Heirloom varieties tend to have less disease resistance.
The pollen of most tomato plants becomes sterile at
90° F and tomato production often ceases during hot periods.
Pollen of some varieties, however, remains fertile at higher
temperatures and those plants set fruit over a longer period
of time in the American Southwest.
Some produce tomatoes the entire summer.
The following tomato varieties set fruit above 90°F.
Cherry-sized Nichols, Prescott and Punta Banda.
Medium-sized Flamenco and Homestead 24. Less popular flavor
varieties Azteca and Super Sioux.
Determinate and Indeterminate
Determinate tomato plants grow to a certain size and
then quit. They produce most of their crop at one time and
are suitable for canning. Indeterminate plants are true vines
and continue to grow. Their crop is produced over the entire
season and great for home gardeners who want to pick fresh
tomatoes every day.
Days to Maturity
Early ripening tomato varieties may produce fruit in as
little as 50 days after pollination. Early Girl, a popular
variety, is one of the quickest to ripen. Most
early tomatoes, though, were developed for cooler, northern
climates and shut down production in summer heat.
Beefsteak varieties can take up to 85 days to ripen. Indeterminate
cherry and "current" sized tomatoes often grow in
bunches and are more likely to have ripe tomatoes ready to
pick every day.
Use Raised Garden Beds or Large Containers
Having a raised garden bed provides better moisture
control. The soil and roots of growing plants will not get
waterlogged during heavy rains. Complaints that raised garden
beds overheat in the southwest can be addressed by providing
afternoon shade to the garden and sides of the raised bed.
Raised beds also make it easier to leach excess salts out of
soil in the desert southwest through rain and watering.
A seven- to ten-gallon container can also be used,
providing it is white or always shaded so the roots are not
overheated. Drill four holes at the bottom of the sides for
drainage unless there is a bottom hole raised off the ground.
Do not use a saucer for the container unless it is placed
upside-down or does not hold water.
Tomato plants should be rotated yearly. Divide your
garden into four equal-sized sections. No garden section
should grow nightshade family members (tomato, eggplant,
chili or pepper, tomatillo, potato, petunia, tobacco) more
than once every four years.
In other words, three-fourths of your garden should NOT
be growing nightshade family members in any given year. Position
all nightshade family members so that together they occupy only
one-fourth of the garden.
This will prevent the accumulation of diseases in the soil
that attack nightshades.
Tomato plants can tolerate a soil pH range of 6.0
(acidic) to 7.5 (slightly alkaline). For information on soil
preparation and soil pH, see
Space tomato plants at least 24" apart and give them
6 square feet of space each. Planting closer together than 24"
promotes fungal diseases. For shallow, raised garden beds,
a 36" separation will provide more room for roots to grow
without competing. Some varieties, especially indeterminates, will
spread sideways even with a tomato cage and need at least 36"
Some gardeners set out seedlings a month or more before the last
frost date to get an early start on tomato production. When freezing
temperatures are predicted, a ring of water-filled 2-liter soda bottles
or tall water bottles are placed around the plants. Floating Row Cover
or a plastic sheet with small holes is then placed over the top of the
plant and the bottles until the temperature rises.
A commercial product, Wall O' Water, can also be used, but is tedious
to set up and seems more appropriate for northern climates.
Planting for Fall
In parts of the desert southwest, gardeners often grow vegetables fall
to spring, then stop during the hot summer. Tomatoes, however,
are sun-loving plants and do best if planted in the spring.
Indeterminate cherry-sized tomatoes are more likely to ripen well
into fall. Current-sized tomatoes will grow in January in Zone 9. For those
getting a late start on planting tomatoes, the most prudent last
planting date for fall crops is July 31 for early-ripening medium to large
sized tomatoes; August 31 for cherry tomatoes, and September 30 for current
Transplanting Potted Plants
Put tomato seedlings in the ground when the danger of frost has nearly passed.
Be prepared to protect from late frosts. Remove the entire pot, whether
peat moss or plastic. Peat moss pots do not rot in our dry soil and retard root growth,
regardless of claims that roots can grow through them.
Place tomato seedlings so that the top of the potted soil is level
with the garden bed soil. This achieves the fastest, strongest growth.
Some nurseries include instructions to place 2/3 of the seedling stem
below ground. That will cause the seedlings to go into shock for the
first month, and barely grow, but they will eventually recover and catch
up to the others.
Tomato plants do best with support if they need to be grown in
Cylindrical cages made of field fence, or concrete reinforcing mesh,
about 19" in diameter and 3 to 4' tall, with 6" long wire spikes on
the bottom to anchor them into the soil, are recommended.
Concrete reinforcing mesh can also be used like a fence. Attach
it, or field fencing, to steel T-posts. Tie vines loosely along the fence.
Check the ties periodically to ensure stems are not being constricted.
Remove All Flowers for the First Four to Six Weeks
Prevent the plant from growing tomatoes by cutting off all flowers
and fruit for the first four to six weeks after transplant.
This will force it to put its energy into growing roots, leaves and stems.
When you do allow flowering and fruiting, the plant will be large enough to grow
more tomatoes. The total fruit yield for the year will be greater.
Sun and Shade
The tomato, like any summer fruit or vegetable plant,
needs sun. How much sun depends on geographic location,
temperature and time of year.
In the American Southwest, 6-8 hours of full sun plus 50-60%
shade in the afternoon is recommended when temperatures are
under 90°F. Growing tomatoes in partial shade reduces water
loss and sun scald and cools the plants so that they will be
more likely to set fruit in the hottest part of summer.
Latticework, sun shade cloth suspended 8' high, or tall plants
can be used to shade the garden.
It should be noted that too much shade in cool
temperatures can increase the likelihood of fungal diseases in
susceptible varieties. On the other hand, when temperatures are
over 90°F, provide 50% shade all day to give tomato plants
a better chance of setting fruit.
By the first of September, the sun will be lower in the
sky and there will be fewer hours of daylight. Provide more sun
by removing overhead shade. By the first of October, eliminate
Water in the morning at the same time every day with the same amount of water.
Check to make sure that 24 hours later, the top one or two inches of soil is dry.
If you are using containers or raised garden beds, and it rains, water as though
there was no rain, or reduce water by no more than 25%. Water will reach the depth
required and excess water will drain off.
Avoid watering in the late afternoon or evening because this encourages fungus
infections in the soil. Also avoid getting water on leaves because this promotes
leaf fungal infections in susceptible varieties, especially when mornings are
Inspecting for Insects
Be sure to inspect closely for any insect activity. Pick off any insects found.
Hornworms can look exactly like rolled-up, green leaves from the side. Inspect
plants at midnight or very early morning for hornworms which feed on the outer
plant at night and move to the interior of the plant during daylight.
Aphids can be removed by jets of water.
One exception — leave the red
caterpillars alone. If they are on your garden cage or tomato support,
they are merely looking for a place to pupate and will be a green or yellow
chrysalis by the next morning. They don't eat human food plants anyway.
Pests and Plant Placement
When all plants of a given species are planted in the same place, insect pests
have an easy time finding them and making a general feast of the neighborhood. This
is called mono-cropping and should be avoided in the vegetable garden.
To confuse insect pests, place a variety of plant species throughout the garden
in seeming random fashion. It will not be truly random, because we must know which
plants go well together and which plants do not.
Placing plants in a vegetable garden is almost like seating guests at a dinner table.
Surround tomatoes with companion plants that ward off
pests and attract beneficial insects. Basil and marigold are
great companions for tomatoes. The aroma of Sweet Basil
repels hornworm moths. Flowering basil attracts
bees. One basil plant is needed for each tomato plant.
French marigold flowers, more than regular marigold,
attract hoverflies, which prey on aphids. Marigold
roots kill nematodes in the soil if planted the season before
tomatoes are introduced.
Other good companions of tomatoes are onion and sage.
Some flowering plants may have to be grown
in pots or separate garden beds to avoid interference with the
tomatoes. Geraniums grown in pots are used as trap crops,
luring aphids and leafhoppers away from other plants.
In one report, geraniums are said to repel tomato fruitworm
moths, although this needs to be verified.
Sweet Basil is a warm weather plant. Seedlings can be
damaged by nighttime temperatures under 50°F and must be
planted a few weeks later than tomatoes. Once basil has been
in the ground four months, it tolerates temperatures in the low
40's. Sweet Basil has the strongest aroma and best hornworm moth
deterrence value of the basils.
Plants that do harm to tomatoes should not be grown in
their vicinity. Some bad companions release chemical compounds
into the soil that harm tomato plant growth or fruiting.
Others vigorously compete for the same nutrients. Beans, dill,
fennel, kohlrabi and potato are bad companions. Corn is also a
bad companion because corn and tomatoes both share a common
parasite: the corn earworm, also known as the tomato fruitworm.
For those reasons, tomatoes should not be planted where bad
companions grow or grew the previous year.
Growing tomatillos is like growing tomatoes with one
difference. Some tomatillo varieties are not self-fruitful and
two or three others must be flowering nearby for pollination.
The fruit is ripe when the husk splits or when the husk is
well filled out and the fruit begins to soften.
Tomato Plant Problems
All Foliage, No Flowers
This occurs when the plant has been given too much
nitrogen. Ammonium sulfate may have been used to acidify
the soil. Ammonium sulfate is a high nitrogen fertilizer and
should not be used with tomatoes. Also, you may want to avoid
rotating tomato plants into a garden bed where nitrogen-fixing
legumes have been grown the year before.
The immediate solution is to sprinkle one-half to one
tablespoon of superphosphate pellets, once only, on the ground
under the plant. Daily watering will gradually dissolve the
phosphate and make it available to the roots.
This should induce flowering within two weeks.
Many Flowers, No Fruit
This normally happens when the tomato variety cannot set
fruit in high temperatures. At times the blossoms on top of the
plant will fail, but those in the shady middle, bottom or north
side will set fruit.
If there is no pollinator, place blooming flowers nearby
to attract bees. Pollination by hand is easy.
Just tap the stem behind the blossom and it will self-pollinate,
assuming that the temperature is suitable.
Dark Brown Spot on Bottom
A dark brown, leathery spot on the bottom of a tomato is
called Blossom End Rot. The causes are inconsistent
watering, insufficient water, cutting roots during
weeding, or insect damage to the stem or the
fruit. Any of these will result in poor calcium ion distribution
inside the plant. Insect damage sometimes results in early fruit
ripening. Another cause is growing a tomato variety which grows
its roots slowly and requires twice the amount of water until the
roots catch up. Some tomato varieties are more prone to blossom
end rot than others.
To avoid Blossom End Rot, inspect for, and remove, any
caterpillars or other insects. Water every day at the same time
with the same amount of water.
At least 6-8 cups of water is needed per plant. Be sure to mulch
the soil around the plant to retain moisture. This is not a
calcium deficiency in the soil but rather a problem with the
transport of calcium within the plant.
American desert Southwest soils have sufficient calcium.
Split Skin and/or Scarring
Split skins and scarring are caused by irregular
water amounts, especially too much water.
Know how much water the plants are getting every day. An increase
in daytime temperature can cause tomatoes to grow faster,
resulting in higher water needs. Sporadic heavy rains may cause
split skins in spite of your best efforts. Assuming no rain,
the top one to two inches of soil should be dry 24 hours after
watering. Some tomato varieties are more prone to skin splits
Fruit Ripen Too Small
Two possible causes:
 The plant is not mature
enough to have the leaf area and root length required to support
the number of tomato fruit in production.
 Too much competition from the roots of other nearby
plants in a garden bed or not enough soil in the container.
Containers should hold at least 7 gallons of soil for each plant.
Tomatoes grown in raised garden beds one foot deep should have
at least 6 square feet of space to themselves, excluding nearby
Cut back on the number of fruit allowed to develop at
one time until the plant grows larger. Never remove leaves from
the plant. They provide energy for growth and needed shade for
Holes in Fruit
This discussion assumes that the tomato plants are
protected from birds.
Small holes, often one-eighth to one-quarter inch in
diameter, are caused by tomato fruitworms. Much larger
holes are often caused by grasshoppers.
Fruitworm and other caterpillar eggs can be controlled with
Green Lacewing larvae. Once caterpillars appear,
Bacillus Thuringiensis is recommended.
An effective defense for grasshoppers is to spray green
and ripening tomatoes with a garlic-pepper solution before they
are eaten. The solution is easy to make. Place four Habanero
peppers and four large garlic cloves in a blender
and mince. Blend in two cups of water and let stand out of
direct sunlight at room temperature for one day.
Strain into a 24 ounce spray bottle with water added to fill.
The solution must be re-sprayed after every rain.
Large Whitish Spot on Fruit
The whitish spot is called Sun Scald. Sometimes there
will be a smaller center of wrinkled skin inside the whitish
spot. This condition is caused by too much direct sun.
The best solution is to give the tomato plant afternoon shade
and avoid removing any leaves.
Yellow Shoulders or Patches on Fruit
Tomatoes with yellow shoulders or patches may also have
a green area inside the yellow. This condition has two main
 The soil is deficient in potassium.
Add compost to the soil before planting or use tomato
fertilizer according to directions.
 When leaves have dark spots that spread to stems
and form cankers and the fruit has yellow blotches, this is
spotted wilt virus spread by thrips. There is no
effective treatment except to cut down the plant and discard
it. Do not put it into a compost pile to avoid spreading the
Fruit Do Not Ripen
Some tomato varieties take a long time for each fruit
to ripen, up to 85 days. Know what is normal for your
variety. If a plant has been ripening fruit but stops doing
so many months after planting, the cause is less
sunlight at the end of summer, especially with many
tomatoes on the plant.
To overcome this, remove all sources of shade and give the
plant full sun if it does not already have it. Cut off all
flowers if it is still producing them. Remove any small green
tomatoes that have not achieved full size.
Reduce daily water to 4 to 6 cups per plant. Cold temperatures
can also slow ripening. When it gets
too cold, the entire plant can be removed from the soil
and placed in a secure, dry place for tomatoes still
attached to the plant to partially ripen. Partly ripened
tomatoes, with a blush of yellow, will finish ripening inside
in a bowl containing apples or a banana.
Tomato Plant Small or Stops Growing
If tomato plants (excluding those grown in pots) are not
over 3' tall after 8 weeks, and there are no disease symptoms,
the likely causes are
 Too much competition from roots of other nearby
plants in a garden bed. Make a choice about which plant
to remove to give remaining plants more separation.
 the soil is deficient in potassium
and possibly other nutrients as well.
In poor fertility conditions, an indeterminate plant can even
stop growing. Tomatoes are heavy potassium feeders. Compost
containing well aged (and watered) manure must be mixed into
the soil in the fall before next year's planting.
 Overwatering can be a problem with dry heat
tolerant tomatoes, especially those that have been in the
ground more than three weeks. This is often accompanied by
yellow leaves. Reduce watering to one-half the usual amount
and see if they grow faster without becoming wilted.
Rust- Bronze-Tinged or Brown Stems or Leaves
Green stems develop a bronze tinge starting from the
ground up. Leaves may quickly dry out without any black or
yellow spots, then become brown and brittle and drop from the
stem. An entire section of stem and leaves may dry out and
turn brown within 24 hours.
The cause is the tiny Tomato Russet Mite, which can
only be seen under 16x magnification. These mites show up
in very dry, hot conditions. They infect nightshade family
plants and are hosted by wild nightshade species such as
Wettable sulfur, sold by nurseries, can be used as a
control. Miticides which contain Pyrethrins and Neem seed
oil are also effective. Follow directions for best results
and do not overuse. Pyrethrins are hard on tomato plants.
Neem seed oil by itself might be better but is very expensive.
Act fast or these mites will destroy
every tomato plant in your garden within days. See
Tomato Russet Mite.
Several factors cause yellow leaves.
Fungal, bacterial and viral diseases may be a
problem, especially with heirloom tomatoes. See
Texas Aggie Tomato Problem Solver. Cut off yellow leaves
with scissors when they occur, and pick up leaf litter on the
garden bed to reduce the spread of any fungus.
Too little or too much water is another possibility.
If leaves are limp in late afternoon, add more water in the
morning. Overwatering can be a problem, especially if plants
are not grown in raised garden beds or in well-draining soil.
Some heat-tolerant plants do not like excessive water even
when loaded with fruit.
Too little sun at the bottom of a bushy plant can result
in bottom leaves turning yellow. This is nothing to worry about.
Insects such as aphids and hornworms can damage
leaves and stems, turning them yellow and even brown. Remove
insects when they are found.
Too little nitrogen in the soil. This is rare in prepared
vegetable garden beds, so test for soil nitrogen content.
Adding a standard tomato fertilizer according to package directions
should solve a nitrogen insufficiency problem.
Insufficient phosphorous availability in the soil results
in reddish-purple stems and leaves. Some tomato varieties may
display leaves colored green on top and purple underneath, with
purple veins. This condition can be caused by a soil pH being outside
the optimum 6.0-7.0 range, so test your soil pH.
For immediate results, use a standard tomato or vegetable
fertilizer as directed, or sprinkle one-half tablespoon of
superphosphate on the ground under the plant and water daily. If
the soil is too alkaline, add two tablespoons of vinegar to each
gallon of water daily.
For long-term prevention, see Soil Preparation.