Arbor

How to Grow Tomatoes

Updated July 2026

Tomatoes need at least 6–8 hours of direct sun per day, consistent soil moisture of about 1 inch per week, and soil that’s warmed past 60°F before you plant. Get those three things right and the variety almost doesn’t matter. Miss any one of them consistently and no amount of fertilizer or pest spraying will compensate.

How it works

Tomatoes are frost-killed at 32°F and struggle below that in ways you can’t always see. Flowers abort when night temperatures drop below 50°F or daytime highs exceed 95°F, so transplant timing is a yield question, not just a survival question. A stall like this is temporary — most plants resume setting fruit once temperatures return to the 55–90°F range. Fruit also needs a thermal window to color correctly: red pigments don’t form above 90°F, so tomatoes ripening in a heat wave come off the vine orange or yellow.

Support, pruning, and harvest expectations all turn on one distinction: determinate versus indeterminate. Determinate (bush) types top out at 1–5 feet, ripen their fruit in a 4–6 week window, then stop. Indeterminate (vining) types run 5–8 feet and keep setting fruit until frost.

Blossom-end rot and fruit cracking are the two problems home growers most often blame on soil or weather, when the root cause is almost always inconsistent watering. NC State and Rutgers agree erratic soil moisture triggers both — soaking after a dry spell stresses the fruit. Calcium deficiency plays a role in blossom-end rot, but the calcium was already in the soil; inconsistent moisture kept the roots from taking it up. Fruit already showing rot or cracks won’t recover, so pull it; once your watering stabilizes, new fruit sets clean. See blossom-end rot on tomatoes for the full picture.

What to do

Start seeds or buy transplants. From seed, sow 5–6 weeks before your outdoor planting date, 1/4 inch deep in sterile soilless mix. Hold 80°F for germination, then drop to 65–70°F once seedlings emerge. The ideal transplant is 6–10 inches tall with 5–7 leaves. Starting indoors buys roughly 4 weeks over direct seeding.

Prepare the soil before you plant. Work 2–3 inches of compost into the top 6–9 inches and target a pH of 6.0–6.8; without a soil test, Rutgers recommends 5–10 pounds of ground limestone per 100 square feet, worked in a few weeks ahead. At planting, apply a starter solution — NC State calls for 3–4 tablespoons of 8-8-8 or 10-10-10 per gallon of water, limited to 1 cup per transplant.

Plant deep, then space for your method. Bury the stem right up to the lowest leaves; roots form along the buried portion and the plant establishes faster. Spindly transplants can go in on their side in a 2–3 inch trench with only the top leaf cluster showing, and cover any peat pot with at least 1 inch of soil. For spacing, staked indeterminate plants want 1.5–2 feet apart; caged plants want 2–3 feet, both in rows 3–4 feet apart. Determinate types can go 1.5–2 feet apart. Set stakes 6 feet tall, driven 8–10 inches deep before the roots spread and 3–5 inches from the stem. For wire cages, 5.5 feet of concrete reinforcing wire in an 18–20 inch circle works well.

Water consistently and at the base. Soak 6–8 inches deep at roughly weekly intervals rather than shallowly every day. Baseline is 1 inch per week; NC State recommends 1.5 inches during active fruiting, and arid Western gardens run 1.5–2 inches. Water at the base — overhead irrigation splashes soil onto leaves and spreads Septoria leaf spot and early blight.

On an established plant, wilting that persists into evening, yellowing lower leaves, or dropped flowers usually points to water, not disease. Probe the soil 2 inches down before reaching for a spray; if it’s dry, lengthen the soak rather than watering more often.

Fertilize when fruit sets. Once first fruits reach about 1 inch across, side-dress 1/2 cup of 5-10-5 or 2–3 tablespoons of 8-8-8 per plant, 4–6 inches from the stem, and again at first harvest. Shift away from high-nitrogen formulas after set — excess nitrogen grows a larger plant with fewer tomatoes.

Prune suckers on indeterminate plants. Remove suckers before they reach 3 inches; on staked plants this keeps the vine manageable and concentrates energy. Determinate types need little pruning; if you remove suckers, wait until they reach 2–4 inches.

Mulch after the soil warms. Apply 2–4 inches once the soil is consistently warm. Utah State cautions against mulching too early: cold, wet mulch slows soil warm-up, the opposite of what young transplants need.

When you add your tomatoes in Arbor, the pruning reminders and watering schedule adjust to your soil type and current forecast — so the sidedress reminder lands when fruit actually sets, not on a fixed calendar date.

Zone and season notes

Northern tier (zones 3–4, Minnesota and similar): Start seeds indoors around mid-April and transplant after mid-May when the frost-free window opens. Use short-season varieties in the 49–50 day range to harvest before September frosts. Early Girl (50 days) and similar extra-early types were bred for this constraint.

Midwest (zones 5–6, Iowa and similar): Transplant early to mid-May. Iowa State sets a hard cutoff of June 20 for last planting — anything later won’t mature before fall frost.

Mountain West (zones 5–7, Utah and similar): Wait for confirmed soil above 60°F before transplanting. Plan for 1–2 inches of water per week — more than the Midwest baseline, because dry Western air pulls moisture from soil faster. Delay organic mulch until soil exceeds 75°F.

Hot climates (zones 9–11, Southwest and Southeast): Expect flowers to drop above 90–95°F, with fruit set stalling for weeks in midsummer heat. Plant in early spring for a harvest before peak heat, or in late summer for a fall crop; a plant that stalls in July is not failing and typically resumes as nights cool. Choose heat-tolerant varieties, and expect fruit ripening during heat waves to show orange rather than full red. Catfaced fruit — scarred at the blossom end from cold-disrupted pollination — is safe to eat; so is fruit with minor cracking.

All regions: To set your last transplant date, count your variety’s days to maturity (49–85 days across the common range) back from first fall frost — Iowa State’s June 20 cutoff is that same math on a short Midwest season. Pick all fruit before frost; green tomatoes ripen indoors at 60–65°F. Store ripe fruit at room temperature for 5–6 days. Refrigerating before full ripeness kills flavor compounds — cold is the one thing a ripe tomato can’t recover from.

Sources

  • University of Minnesota Extension — Growing Tomatoes in Home Gardens — extension.umn.edu/vegetables/growing-tomatoes
  • NC State Extension — Growing Tomatoes in the Home Garden — content.ces.ncsu.edu/growing-tomatoes-in-the-home-garden
  • Rutgers NJAES — FS678: Growing Tomatoes in the Home Garden — njaes.rutgers.edu/fs678/
  • Utah State University Extension — How to Grow Tomatoes in Your Garden — extension.usu.edu/yardandgarden/research/tomatoes-in-the-garden
  • Iowa State University Extension — Growing Tomatoes in the Home Garden — yardandgarden.extension.iastate.edu/how-to/growing-tomatoes-home-garden