How to Grow Tomatoes

Tomato indeterminate on tepeesTomatoes are a warm-season annual that grow best when the soil temperature is at least 55°F (12°C) and the air temperature ranges between 65° and 90°F (18-32°C). Tomatoes require from 50 to more than 90 warm, frost-free days to reach harvest. Tomatoes are commonly grown from seedlings started indoors and transplanted into the garden. Start tomato seed indoors as early as 8 to 6 weeks before the average date of the last spring frost. Garden soil is usually warm enough for tomato transplants 2 to 3 weeks after the last frost. If an unexpected frost threatens, transplants must be covered and protected.

Description. The tomato is a tender subtropical perennial grown as annual. Tomatoes are weak stemmed with vining or sprawling habits depending upon the variety. Tomatoes have alternate lobed and toothed leaves. Yellow flowers grow in clusters either along stems or at the end of stems. Depending on the variety, fruits vary in size from marble-sized to apple-sized and in color from red to yellow to orange to white. Some tomatoes may be green or purple-black.

Tomatoes can be divided into two main groups according to growing habits: determinate and indeterminate.

A determinate or bush tomato flowers at the end of its stalks. When the determinate tomato flowers it stops growing–usually at about three feet tall. Flowers then set fruit. Fruit grows and ripens usually all at once over a four- to six-week period. Determinate tomatoes often sprawl and do best with some support.

An indeterminate or vine tomato produces a succession of flowers along its branching spurs; fruit forms from those blossoms. The end buds of indeterminate tomatoes do not set fruit like determinate tomatoes. Indeterminate tomatoes will grow almost indefinitely if not pruned or stopped by frost. Some can reach 14 feet (4.2 m) tall or taller if the growing tips are not pinched back. Most indeterminate tomato varieties require staking or caging.

Tomato classifications. Tomatoes are further classified by the size and shape of their fruit: currant, cherry, plum, pear, heart-shaped, oblong, oblate, and round. Tomatoes are classified by their color: red, pink, orange, yellow, cream, white, green, purple to black, and zebra-striped multi-colors.

Tomatoes also can be classified by when they come to harvest: early season (from 40 to 60 days); midseason (60 to 80 days); and late season (80 or more days). Some tomatoes are picked green and ripened indoors.

Tomatoes also are classified by their use: slicing and fresh eating, canning, pickling, and sauce, paste, and cooking.

Tomatoes often are selected by where they will fit and grow in the garden:

Dwarf and container tomatoes (mostly determinate varieties) require the least amount of space. They can be grown in a small-sized garden–just a square foot or two–or in a container with just two to three cubic feet of soil. Hanging basket or window box grown tomatoes must not be allowed to wilt or go dry.

Vining tomatoes are best staked or caged to support long stems and fruit. Indeterminate tomatoes can be left to sprawl naturally on the ground but fruit may become susceptible to diseases and be more difficult to find and pick at harvest time. Sprawling tomato fruits will require less work at the outset but are best grown on a mulch to keep fruit clean and reduce disease. All tomatoes grown in wet or humid conditions are best staked or caged to allow for ample air circulation and the drying of leaves and fruit.

Staked and trellised tomatoes require tying in place and pruning. A staked tomato requires the least amount of growing space. But tying and pruning decrease the number of fruiting stems and blossoms. Fruit will be clean at harvest time.

Caged tomatoes require the least amount of work. Cages are commonly set in place when a plant is young so that it can grow up and into the cage. Caging, like staking, allows tomatoes to be grown in tight spaces, fruit is kept up off of the ground and open to air circulation. Caged tomatoes may or may not require pruning.

Yield. Plant 1 to 4 tomato plants for each household member. Consider the variety and how the tomato will be used: eating fresh, cooking, canning or preserving. Mix early and late cultivars or determinate and indeterminate tomatoes to allow for a staggered and continuous harvest. Double the number of plants if you plan to crush the fruit for juice.

Site. Grow tomatoes in full sun. Tomatoes require warm, well-drained but moisture retentive soil rich in organic matter. Tomatoes will produce earlier in light, sandy soil, but the yield will be greater in heavier, loamy soil. Add aged compost to planting beds in advance of planting. Tomatoes prefer a soil pH of 5.5 to 6.8. Planted in containers tomatoes require the most soil you can provide and good drainage.

Planting time. Tomatoes grow best when the day temperature is between 65° and 85°F (18-29°C). Tomatoes will not grow in soil cooler than 55°F (13°C) and tomato flowers will not set if the air temperature goes below 55°F . Tomatoes will not ripen and turn red if the night temperature goes above 85°F (29°C) and plants will stop growing if the temperature rises above 95°F (35°C).

Starting from seed. Start tomatoes from seed in the garden on the average date of last frost in spring. But commonly, tomatoes are grown from transplants started indoors and set in the garden 2 to 3 weeks after the average last frost date, when the soil has warmed.

Tomatoes require from 50 to more than 90 warm days to reach harvest depending upon variety; the soil temperature must be at least 55°F and optimal air temperatures will range between 65° and 90°F. Start tomato seed indoors as early as 14 to 10 weeks, but more commonly 8 to 6 weeks before garden soil warms to 55°F in spring. Garden soil is usually warm enough for tomato transplants 2 to 3 weeks after the last frost in spring; set young plants out protected from direct sun during the day for two weeks to harden off and acclimatize before transplanting. If an unexpected frost threatens, transplants must be covered and protected.

Planting and spacing. Sow two to three seeds ½ inch deep and 1 inch (2.5 cm) apart. Thin to the strongest seedlings in the week or two after germination. Seedlings should be thinned when they are large enough to handle. Set tomatoes in the garden from 18 to 36 inches (45-91 cm) apart in rows 24 to 48 inches (61-117 cm) apart depending on how large the variety will grow.

Growing indoors. Seed started indoors will germinate best where the bottom temperature is about 85°F (29°C). Keep the soil moist but not wet. Seeds can be started in bright window or under lights set about 2 inches (5 cm) above the plants. Ten days after germination, move seedlings started in flats into 2-inch pots. Nip off all leaves except those at the top then set the seedlings in the new pots up to just below the bottom leaf set. Slip plants gently from their containers. Make every effort not to disturb the roots at transplanting. New roots will grow from the buried stem. Grow young seedlings on at 60° to 70°F (21°C); allow a gentle breeze to rustle over young seedlings each day so that they grow strong stems. About four weeks after germination, about two weeks after potting up seedlings the first time, pot them up again to 4-inch pots. Trim all of the leaves below the top 2 inches of the plant and repot them as before. About two weeks before transplanting into the garden place seedlings in a cold frame or protected area outdoors each day to harden them before transplanting.

Transplanting. If transplants have been grown in peat or paper pots, the plant and container can be placed in the garden. Make sure to break away or bury the tops of biodegradable containers below the soil’s surface or they will act like a wick and evaporate the soil moisture around roots. If transplants are growing in large flats, cut the plants apart several days before transplanting them.

Again when transplanting into the garden, set the young plant deeper than it was growing before, up to the top two sets of leaves. If the stem is very long or spindly, dig a shallow trench in the garden and lay the plant on a slant so that only the leaves are above soil level. Roots will grow from the submerged stem and the stem will quickly right itself and grow straight. Burying stems at transplanting will make for sturdier plants. Set the transplants 18 to 36 inches apart in rows 24 to 48 inches (61-122 cm) apart depending on the variety. Stake or cage vining plants soon after transplanting.

Water and feeding. Tomatoes require regular even watering, between 1 and 2 inches of water every week. Keep the soil moist but not wet. Water thoroughly before the soil dries out. If leaves wilt in the morning, tomatoes need an immediate slow, deep watering. Water at the base of the stem; avoid wetting leaves. Leaves may curl on hot days; this is a way for plants to conserve moisture and is not necessarily a sign of distress.

Prepare planting beds with aged compost before transplanting. Side dress tomatoes with aged compost again at midseason. Blossom-end rot can be the result of uneven watering or a lack of calcium in the soil. Crushed eggshells added to spot watering every two weeks can provide calcium needed. Compost tea applied every two weeks will provide nitrogen and other nutrients needed.

Companion plants. Asparagus, carrots, chives, marigolds, nasturtiums, onions, parsley.

Staking and pruning. Stake tomatoes with six foot stakes (one by two inches) or plastic stakes, or reinforcing rods. Set stakes at the time of transplanting. Staked tomatoes are best pruned so that they grow on a straight stem against the stake. Prune staked tomatoes to one or two stems by pinching out the growing tip of each side branch after it has sprouted at least two leaves. To prune to more than one main stem, choose the stems you want to keep and pinch out the rest; leave a couple of leaves at the base of each side branch or stem you remove. Do not pinch back side shoots until two leaf sets develop; this will provide foliage cover from sunburn for fruits and stems later. Note that pruning will reduce the total crop and is likely to increase the incidence of blossom-end rot.

Tomato cages. Cage determinate tomatoes to keep them from sprawling and cage indeterminate tomatoes to support their upward growth. Use a 18-inch/46 cm-diameter cage for small, bush tomatoes. Use a 24-inch/61 cm-diameter cage to support large, vining tomatoes. Round or square cages can be bought ready made; square cages are easily folded and stored. To make your own cage use 6 by 6 inch (15×15 cm) mesh reinforcing wire. A five foot width cut five feet long and bent into a cylinder and tied off will support a six-foot tall tomato plant. Remove the bottom horizontal wire and push the cage into the ground six inches deep surrounding the tomato plant. Add a supporting stake in windy areas.

Trellises can be used to support tomatoes. Fashion a trellis out of 6 by 6 inch galvanized mesh. Stretch the mesh between two stakes set about 8 feet apart. Tie off the vines as they grow up, similar to staked plants.

Care. Mulch around the base of tomatoes with aged compost to slow soil moisture evaporation.

For stronger plants and bigger fruit, pinch out all suckers that start t grow in the crotch of the main stem and side branches. Root the suckers in a starting mix to start a second crop for succession planting.

Night temperatures colder than 55°F or day temperatures above 95°F will keep flowers from setting fruit.

Container growing. Small determinate varieties are easily grown in containers. Grow a single plant in a 12- to 24-inch-deep container depending on the size of the variety at maturity. Provide a stake, cage, or trellis for support at planting to avoid the risk of damaging the growing root later on.

Pay close attention to soil moisture for tomatoes grown in containers. Keep the soil evenly moist.

Move tomatoes in containers indoors if frost threatens. Tomatoes can be grown in containers through the winter indoors.

Pests. Aphids, tomato hornworms, cutworms, tomato fruitworms and whiteflies can attack tomatoes. Place collars around plants at the time of transplanting to help discourage cutworms. Handpick and destroy hornworm and fruitworms. Aphids and whiteflies can be discouraged by hosing off pests with a blast of water or pinch out infested foliage.

Diseases. Tomatoes are susceptible to both viral and fungal diseases including verticillium wilt, fusarium wilt, early blight, Septoria leaf spot, tobacco mosaic virus, and blossom end rot. To stave off disease plant disease resistant varieties and keep the garden clean and free of debris. Verticillium and fusarium wilt can cause tomato plants to suddenly wilt, turn brown, and die, usually in a week or less. Mosaic virus or herbicide injury can cause tomato leaves to grow distorted, twisted, and stunted. Grow resistant varieties. Keep water off of leaves and avoid handling plants when they are wet. Tomatoes are a relative of tobacco and can be attacked by tobacco plant diseases such as tobacco mosaic virus; wash your hands thoroughly before working with tomato plants if you smoke. Remove diseased plants from the garden immediately before disease can spread.

Disease-resistant varieties are identified by a letter code which will be found on seed packets or transplant identification stakes: “V” (verticillium wilt), “F” (fusarium wilt), “N” (nematodes–microorganisms that cause root cankers); and “T” (tobacco mosaic virus). Check with a nearby garden center or master gardener organization to select varieties that are most resistant to persistent disease in your area. Use resistant varieties if crops in your garden have been diseased in the past.

Rotting at the blossom or bottom end of the fruit is called blossom end rot. This is commonly caused by fluctuations in soil moisture. To control blossom end rot, water regularly and use a mulch around the plants.

Harvest. Tomatoes will be ready for harvest from 40 to more than 100 days from transplanting depending on variety. Add 4 to 6 weeks longer from seed.

Color at harvest depends on the variety. Pick tomatoes when the color is full and size is reached. Support the vine or stem in one hand and lift and gently twist the fruit away from the vine with the other. Ripe tomatoes should be firm but not too soft or too hard. Green tomatoes can be harvested and ripened indoors on the counter. Green, unripe tomatoes can also be fried or pickled.

Varieties. There are thousands of varieties of tomatoes; several hundred named varieties are readily available as seed or starts. Choose plants to grow based on:

  • How you plan to use the fruit after harvest: fresh eating, cooking, canning, preserving, or drying. Choose beefsteak and slicing tomatoes or cherry or miniature tomatoes for fresh eating; choose paste or cooking tomatoes for cooking
  • The length of your growing season: early, main crop, or late harvest.
  • The size of the plant you can accommodate in your garden or container.
  • Whether you plan to stake or cage the plant or let it sprawl.

Storing and preserving. Ripe tomatoes will keep in the refrigerator for up to one week. Tomatoes also can be frozen, canned, or dried whole or sliced. Tomatoes can be made into juice, paste, relish, or pickles. Green tomatoes harvested before the last frost can be set in a cool, moist, place for up to one month as they ripen.

Common name. Tomato

Botanical name. Lycopersicon esculentum

Origin. Tropical America