Overview

Tomatoes (scientific name Solanum lycopersicum) are members of the nightshade (Solanaceae) family. Other members of this family are chili, including Bell pepper, eggplant, golden berry, petunia, potato, tobacco, and tomatillo.

Selecting Tomato Varieties

Disease Resistance
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.

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.

Heat and Sun Tolerance
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 Southwestern United States. Some produce tomatoes the entire summer. Varieties optimized for heat in the Southeastern United States, however, are often accustomed to greater cloud cover and do not adapt well to the Western United States where there are few clouds and direct hot sun all day.

Heat Tolerant Tomato Varieties
Tomato varieties that set fruit above 90°F. include cherry-sized Nichols, Prescott and Punta Banda; and medium-sized Flamenco and Homestead 24.

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.
Indeterminate cherry and "current" sized tomatoes often grow in bunches and are more likely to have ripe tomatoes ready to pick every day.
Beefsteak varieties can take up to 85 days to ripen.

Cultivation Practices

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 southwest desert 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.

Rotating Crops
Tomato plants should be rotated yearly. Divide your garden into four equal-sized sections. No garden section should grow nightshade family members (tomato, chili, including Bell pepper, eggplant, golden berry, petunia, potato, tobacco, and tomatillo) 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.

Soil Preparation
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 Soil Preparation.

Spacing
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" separation.

Planting Early
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 southwest desert, 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 sized tomatoes.

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.

Planting Depth
Bury the tomato seedling stem up to the first true leaf on the stem. Remove any leaves on the stem that touch the soil. This will achieve the fastest, strongest growth and produce the highest yield. 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.
It should be noted that tomatoes are one of the few plants that can be treated this way. Nearly all shrubs and trees need their root crowns to be at or slightly above ground level.

Support
Tomato plants do best with support if they need to be grown in confined spaces. 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 shade altogether.

Watering
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 cool.

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 Pipevine Swallowtail 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 chrysalis by the next morning. They don't eat human food plants and add interest to the garden.

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.

Good Companions
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.

Bad Companions
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.

Tomatillos: Physalis ixocarpa and Physalis philadelphica

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 are ripe when the husk splits or when the husk is well filled out and the fruit begins to soften.