How to Grow Tomatoes from Seed: From Sowing to Harvest
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Nothing tastes like a homegrown tomato. The difference between a sun-warmed tomato picked at perfect ripeness and anything from a store shelf is the reason so many gardeners start seeds every spring. Growing from seed — rather than buying transplants — also opens up hundreds of varieties you will never find at a garden center: striped heirlooms, tiny currant types, rich black beefsteaks.
Tomatoes come in two growth habits worth knowing. Determinate (bush) types grow to a set size, ripen most of their fruit in a concentrated window, and are great for canning. Indeterminate (vining) types keep growing and producing until frost, and they need sturdy staking. The sowing steps below work for both.
What You'll Love About Growing Tomatoes
Flavor is the headline, but variety choice is the real joy of seed starting: you can grow exactly the tomato you want to eat. Indeterminate varieties give you a steady harvest for months from just a few plants. Tomatoes are also generous teachers — they germinate readily, grow fast, and respond visibly to good care, making them deeply satisfying for beginners and old hands alike.
Explore options in our vegetable seed collection.
How to Sow Tomato Seeds
Timing
Sow indoors 6 to 8 weeks before your area's last spring frost. Starting earlier rarely helps — oversized, leggy transplants usually perform worse than younger, stockier ones.
Sowing Depth
Plant seeds 1/4 inch deep in a sterile seed-starting mix, in cells or small pots. Cover lightly, water gently, and keep the mix consistently moist but not waterlogged.
Soil Temperature
Warmth is everything at this stage. Seeds germinate best at 75 to 90°F and usually emerge in 7 to 14 days; at cooler temperatures they sprout slowly or unevenly. A heat mat makes a real difference. Once seedlings are up, move them off the heat and grow them on at around 65 to 70°F.
Light
The moment seedlings emerge, give them strong light — a sunny south-facing window is barely adequate, and a simple grow light positioned a few inches above the plants for 14 to 16 hours a day produces much sturdier transplants. Rotate trays daily if you rely on window light.
Transplanting Outdoors
Wait until all danger of frost has passed, the soil has warmed to at least 50 to 60°F, and nighttime temperatures stay above 45 to 50°F. Cold soil stunts tomatoes badly — plants set out in warm soil usually catch up to and pass earlier-planted ones. Harden seedlings off over 7 to 10 days by gradually increasing their outdoor exposure.
Plant tomatoes deeper than they grew in their pots: bury the stem up to the first set of true leaves. Unlike most plants, tomatoes sprout roots all along a buried stem, giving you a much stronger root system.
Spacing and Site
Choose the sunniest spot you have — 6 to 8 hours of direct sun minimum. Space determinate types 12 to 24 inches apart, staked indeterminates 18 to 24 inches apart, and unstaked indeterminates 24 to 36 inches apart, with rows at least 3 feet apart. They want rich, well-drained soil with a pH around 6.0 to 6.8; work compost into the bed before planting.
Caring for Tomato Plants
Watering. Water deeply at the base, keeping foliage as dry as possible — wet leaves invite blight and other diseases. Mulch with straw or shredded leaves to hold moisture and prevent soil splashing onto lower leaves. Aim for consistent moisture; erratic watering (soak, then drought) causes fruit cracking and encourages blossom end rot.
Support. Stake, cage, or trellis plants early, before they need it. Both determinate and indeterminate types do best with fruit held off the ground.
Pruning. On indeterminate varieties, pinching out suckers (the shoots that appear in leaf axils) improves airflow and directs energy into fruit. Determinate types generally need no pruning.
Feeding. A balanced fertilizer at planting and again when fruits begin to set is usually enough. Go easy on nitrogen — too much grows a jungle of leaves with few tomatoes.
Pests and rotation. Watch for hornworms, aphids, and whiteflies; handpicking and strong blasts of water handle most problems. Don't plant tomatoes where tomatoes, peppers, potatoes, or eggplants grew last year, to break disease cycles.
Harvesting Tomatoes
Pick when fruits show full color for their variety and give slightly to gentle pressure. If frost threatens with green fruits still on the vine, bring them indoors — most will ripen on the counter at room temperature (never refrigerate fresh tomatoes; cold kills their flavor). Keep picking ripe fruit promptly; it signals the plant to keep producing.
Common Mistakes to Avoid
- Starting seeds too early. Leggy, root-bound transplants underperform younger ones.
- Transplanting into cold soil. Wait for genuinely warm soil and nights.
- Planting at pot depth. Bury that stem — it's free root system.
- Overhead watering. Wet foliage is an invitation to disease.
- Inconsistent watering. Regular, deep watering prevents split fruit and blossom end rot.
- Too much nitrogen. Lush leaves, little fruit.
Worth Every Step
From a 1/4-inch seed to armloads of tomatoes is one of gardening's great transformations — and starting your own means the variety choice is entirely yours. Once your tomatoes are in, try their warm-season companion: read our guide "How to Grow Peppers from Seed" next.