How to Grow Tomatoes

Pick a type that fits your season

The single biggest decision is the variety, because it sets how early you eat, how much support the plant needs and whether it can set fruit in your summer.

Determinate tomatoes grow to a fixed size, usually 3 to 4 feet, set most of their fruit over a few weeks and then decline. Most early-ripening varieties are determinate. They suit short seasons, containers and anyone who wants a big batch for canning at once. Indeterminate tomatoes keep growing, flowering and ripening fruit until frost and can reach 7 to 12 feet, so they need tall stakes or a trellis. Most heirlooms are indeterminate. Semi-determinate types fall in between.

Then read the tag for disease codes. V means resistance to Verticillium wilt, F to Fusarium wilt (FF and FFF cover more races), N to root-knot nematodes, T or ToMV to tobacco or tomato mosaic virus, and TSWV to tomato spotted wilt virus. Clemson notes that most heirlooms carry little or no resistance, which is why they struggle where soil diseases are established.

Varieties that extension services recommend for their own regions:

• Maine and northern New England: University of Maine lists Early Cascade, New Girl and First Lady as extra early, Sun Gold, Matt’s Wild, Juliet and Sweet Million for small fruit, and Bellstar and San Marzano for paste. In northern Maine it advises growing only early varieties.
• Western Oregon and the Pacific Northwest: Oregon State’s trials in Corvallis list determinate slicers such as Oregon Spring, Siletz, Legend and Santiam. Siletz, Legend and Santiam were bred at the university and are parthenocarpic, meaning they can set seedless fruit when it is too cool for normal pollination.
• Texas: Texas A&M suggests Better Boy, Big Beef, Celebrity, Carnival and Bush Beefsteak for large fruit and Juliet, Small Fry and Cherry Grande for small fruit.
• Florida: UF/IFAS lists Heat Wave II, Celebrity, Better Boy and several TSWV-resistant hybrids such as Amelia, BHN 602 and Bella Rosa, and notes that cherry types handle heat well.
• Hot inland California: UC Cooperative Extension advises skipping varieties with “Beef” in the name, which set fruit poorly in the heat of the inland valleys.
• Utah and other curly top areas: Utah State recommends Roza, Columbia, Rowpac or Saladmaster where the leafhopper-spread curly top virus is a known risk.

Starting seeds or buying plants

Buying transplants is easiest for a few plants. If you grow your own, sources differ on timing: Clemson says to sow 6 to 8 weeks before your last frost, NC State’s plant profile says 5 to 6 weeks before planting out, and Oregon State says 5 to 8 weeks depending on temperature. Older plants are not better; Utah State notes that transplants that carry flowers or fruit establish slowly and yield poorly, so pinch those off before planting.

Seed sprouts in about 6 to 8 days when the mix is 65 to 85°F. At 50°F it can take more than 40 days, which is why a cold windowsill gives patchy results. Utah State germinates seed at 80°F, then grows seedlings at 65 to 70°F under fluorescent tubes hung 2 to 3 inches above the leaves for 14 to 16 hours a day. Too little light is the main cause of tall, spindly transplants.

Aim for stocky, dark green plants 6 to 10 inches tall with 5 to 7 leaves. Harden them off for about a week before planting: start with a few hours outdoors in bright shade, lengthen the time each day, and water a little less often without letting them wilt. Purple tinting on the leaf veins during this week is normal.

When and where to plant

Plant after the danger of frost has passed and the soil has warmed to at least 60°F; check it with a probe thermometer at planting depth, and use the dates for your zone above as your starting point. Tomatoes planted into cold soil just sit there. Oregon State notes that tomatoes perform best with soil at 65°F or warmer and air above 60°F, and that plants set out into cool, wet weather often look sickly until it warms. Cold during flowering also causes catfaced, scarred fruit on the first clusters.

Sun matters more than almost anything else. Texas A&M and Clemson call for at least 6 hours of direct sun, Oregon State for 7 or more, and UC for 8. Clemson observes that plants with less than 6 hours produce few blossoms. Choose a spot where tomatoes, peppers, eggplant or potatoes have not grown for at least 3 years to starve out soil-borne diseases and nematodes.

Tomatoes do poorly in heavy, wet soil. If yours drains slowly, plant in a raised bed or on beds about 6 inches high, as Texas A&M recommends. Clemson suggests holding the pH between 6.0 and 6.5; NC State suggests 6.5 to 6.7 when blossom-end rot has been a problem. A soil test settles which applies to your garden.

Plant deep. Tomato stems root wherever they are buried, so set transplants with only the top two or three sets of leaves above ground. For leggy plants, NC State recommends stripping all but the top 4 or 5 leaves and laying the stem sideways in a trench, covered with 2 to 3 inches of soil. Grafted plants are the exception: keep the graft union at least 1 inch above the soil, or the top variety will root and lose the benefit of the rootstock. Transplant in the evening or on a cloudy day to reduce wilting, and water in well.

Spacing depends on how you support the plants. Staked plants can go 18 to 24 inches apart, caged plants 3 to 4 feet, and Texas A&M leaves 4 to 5 feet between rows for plants allowed to sprawl. Crowding saves space but keeps foliage wet longer, which favors leaf diseases.

Watering and mulch

Uneven moisture causes most fruit problems, including blossom-end rot and cracking. Utah State recommends 1 to 2 inches of water a week, applied deeply and infrequently. NC State suggests soaking the soil 6 to 8 inches deep every 7 days, and about 1.5 inches a week during fruiting. Oregon State uses a 7- to 10-day interval. In California, where roots may reach 3 feet deep, UC advises watering established plants when the top 2 to 3 inches of soil are dry; depending on soil and weather that can mean anywhere from three times a week to once every two weeks. Drip lines and soaker hoses keep leaves dry, which matters because wet foliage late in the day spreads leaf spots and blight.

Mulch evens out moisture and keeps fruit off the soil, but timing matters. Utah State advises holding off on straw, leaves or grass clippings until the soil is above 75°F, because organic mulch keeps cool spring soil cool. In short-season areas, black plastic laid before planting does the opposite and warms the soil. Oregon State stresses that it must be pressed flat against a smooth soil surface; plastic that billows shades the ground and keeps it colder. Don’t let the stem touch hot plastic. Only use grass clippings from lawns treated with herbicides labeled safe for food crops, since growth-regulator weed killers such as 2,4-D twist and cup tomato leaves.

Feeding

Too much nitrogen is the classic mistake: it grows a huge, leafy plant that flowers late and sets little fruit. Work in fertilizer according to a soil test before planting, then side-dress lightly. The sources give different schedules:

• Clemson: 1 pound of calcium nitrate per 100 square feet three to four weeks after planting, split into two doses on sandy soil.
• Utah State: ½ tablespoon of 21-0-0 per plant at 4 and 8 weeks after transplanting.
• NC State: 2 to 3 tablespoons of 8-8-8 or 10-10-10 per plant once fruit begins to set, then every 4 to 6 weeks.
• Oregon State: one nitrogen application around fruit set and no more.

Clemson’s diseases fact sheet prefers calcium nitrate for side-dressing because ammonium forms of nitrogen, which include most complete fertilizers such as 10-10-10, compete with calcium uptake and can worsen blossom-end rot. Keep fertilizer 4 to 6 inches from the stem and water it in.

Staking, caging and pruning

Supporting the plant keeps fruit off the ground, improves airflow and makes picking easier. Put supports in at planting time so you don’t spear the roots later. Trench-planted tomatoes are easy to stake through by mistake.

• Stakes: 6-foot stakes driven about a foot deep, 3 to 6 inches from the plant. Tie the stem loosely every 10 to 12 inches with cloth or soft twine.
• Cages: NC State makes cages from concrete reinforcing wire, 18 to 24 inches across, and anchors them with stakes. Clemson recommends openings of at least 6 inches so you can reach in to pick. Oregon State warns that the cone-shaped cages sold in stores hold up only the smallest varieties.
• Florida weave: 6-foot stakes between every plant or every other plant, with twine run along both sides of the row and a new strand added about every 10 inches of growth. It suits rows of determinate plants.

On staked indeterminate plants, pinch out the suckers that form where each leaf meets the main stem, keeping one or two stems. NC State says to remove suckers before they reach 3 inches. Caged plants need little or no pruning. NC State notes that staked plants give larger but fewer fruit, while caged plants give the highest yield per plant. Determinate types should only lose the side shoots below the first flower cluster, as the shoots above it carry the crop. Pruning has a cost in hot climates, though: Clemson points out that sparse foliage exposes fruit to sunscald. In short seasons, Oregon State suggests topping indeterminate plants about a month before your first frost so they put their energy into ripening the fruit already set.

How the advice changes by region

Cold north and mountain areas. Your season is the limiting factor, so gain warmth wherever you can: black plastic, row covers, water-filled rings and a planting spot against a south-facing wall. University of Maine says row covers can raise daytime air temperature around plants by up to 10°F. Vent covers above 80°F, and Oregon State advises removing them when plants flower. In cold areas such as central Oregon, Oregon State recommends adding 10 to 14 days to the days-to-maturity on the seed packet and using transplants, not direct seeding.

The humid South and Southeast. Heat and disease are the problems. Fruit set stalls in midsummer, so NC State advises planting as early as your frost dates allow; large beefsteaks are harder to get there for this reason. For heat tolerance, Clemson suggests Arkansas Traveler, Homestead 24, Bella Rosa, Solar Fire or Florida 91. Choose TSWV-resistant types where thrips spread spotted wilt. A second crop is possible in late summer on the coastal plain, and Texas A&M sets fall transplants about 100 days before the first expected frost.

The arid West. In hot inland valleys, heat stops fruit set and also affects color: UC explains that the red pigment fails to develop above about 86°F, leaving fruit yellow-orange. Choose varieties known to set fruit in heat and keep plants leafy to shade the fruit. In the low desert around Phoenix, University of Arizona plants in late winter and again in midsummer, and suggests delaying fall planting until whitefly numbers fall.

Warm-winter areas. In central and south Florida and similar zones 9 to 11, tomatoes are a fall-through-spring crop. Plant so fruit sets before summer heat, not during it.

Common problems and fixes

• Blossom drop. Utah State puts the limits at nights below 50°F or days above 95°F; Clemson uses 55°F and 90°F. UC adds shade, heavy nitrogen, drought and smog to the causes. Heat-caused drop resolves when temperatures ease. UC notes that fruit-set hormone sprays help only in cool weather, not heat.
• Blossom-end rot. Sunken, dark, leathery patches on the bottom of the fruit. Even moisture is the main fix. Lime or add gypsum only as a soil test directs, and skip Epsom salts unless the test shows a magnesium shortage, since magnesium competes with calcium. The first fruits are often worst; later ones are usually fine once watering evens out.
• Cracking. Rapid growth after a dry spell followed by heavy rain or watering. Keep moisture steady and choose crack-resistant varieties; heavy root or vine pruning makes it worse.
• Catfacing. Scarred, misshapen fruit caused by cold during flowering. It affects early clusters and fades as the weather warms.
• Sunscald. Pale, papery patches on fruit exposed to hot sun. Keep foliage healthy and avoid over-pruning.
• Leaf roll. Older leaves curl upward and feel leathery, often under a heavy fruit load, heat or after hard pruning. It looks alarming but does little harm.
• Early blight and Septoria leaf spot. Spots on the lower, older leaves that spread upward. Early blight shows bull’s-eye rings; Septoria makes small spots with tan centers and is most active at 68 to 77°F in humid weather. Water at the soil, mulch, remove infected lower leaves, rotate for 3 years and clear plant debris in fall.
• Late blight. Dark, water-soaked spots that spread fast in cool, wet weather and can strip a plant of leaves within two weeks. Remove infected plants and destroy volunteer tomatoes and potatoes.
• Fusarium and Verticillium wilt, root-knot nematodes. Plants wilt, yellow on one side, or stall with knotted roots. There is no cure once plants are infected, so prevent them with resistant varieties (F, V, N) and rotation. Clemson lists the marigold cultivars Tangerine, Petite Gold and Petite Harmony as a rotation crop that lowers nematode numbers.
• Hornworms, flea beetles and whiteflies. Handpick hornworms or use Bt; insecticidal soap handles soft-bodied insects.

Harvest and storage

Fruit needs about 25 to 35 days from flowering to ripen, depending on temperature and variety. For the best flavor, pick when it is fully colored but still firm. Oregon State notes that fruit can also be picked at the mature-green stage, when the inside has filled with gel, and ripened indoors at 65 to 70°F. Clemson says light isn’t needed.

At the end of the season, pick every mature green and colored fruit before frost. Oregon State warns that fruit left on the vine through several days below 50°F may start to rot. Store ripe tomatoes at 50 to 55°F if you can, and otherwise at room temperature, rather than in the refrigerator. Cold causes chilling injury, a mealy texture and lost flavor. At season’s end, pull out the plants and destroy any diseased ones instead of composting them.