Tomatoes (Solanum lycopersicum) are the most popular crop in home gardens, and nothing from the store compares to a ripe tomato picked warm from the vine. Growing tomatoes from seed gives you access to far more varieties than you’ll find as nursery transplants. This guide covers every step, from starting tomato seeds indoors to trellising and pruning your plants for a healthy, productive harvest. Shop tomato seeds
Tomato growing at a glance
- Sun: Full sun
- When to start seeds: Indoors, 6–8 weeks before your last frost
- Planting depth: 1/8 inch
- Germination: 7–10 days
- Ideal growing temperature: 75–95°F
- Plant spacing: 24 inches
- Frost hardy: No
- Growth habit: Indeterminate
When to Start Tomato Seeds
Start tomato seeds indoors 6–8 weeks before your last expected frost. Tomatoes aren’t frost hardy, so starting them inside gives the seedlings time to grow strong before it’s warm enough to plant them outdoors.
How to Start Tomato Seeds Indoors
- Fill seedling trays with seed starting mix that contains essential nutrients.
- Sow seeds 1/8 inch deep. Barely cover them with soil, since tomato seeds need only a light covering.
- Keep the soil moist for quick, even germination. Seeds sprout in 7–10 days.
- Give seedlings plenty of light. Strong light grows sturdy, healthy stems and leaves. Without enough light, seedlings stretch and turn weak and leggy.
When to Transplant Tomatoes
Transplant tomato seedlings outdoors after your last frost, once the weather has warmed. Tomatoes grow best at 75–95°F, and even a light frost can kill them.
Best Soil and Spacing for Tomatoes
Plant tomatoes in full sun, in well-drained, fertile soil. Space plants 24 inches apart so each one has room to grow and air can move between them.
How to Fertilize Tomatoes
Feed tomato plants with a liquid fertilizer once every two weeks through the growing season.
How to Water Tomatoes
Water tomatoes regularly, especially once the plants start flowering, when steady moisture matters most for setting fruit. Always water at the base of the plant rather than over the leaves, since wet foliage invites disease. A layer of mulch around the plants holds moisture in the soil and keeps soil from splashing onto the leaves.
How to Trellis Indeterminate Tomatoes
Indeterminate tomatoes keep growing and producing fruit all season, sending out long vines that can reach 6 feet or more. Support them with a trellis, sturdy stakes or tall cages to keep the vines and fruit off the ground.
Pruning Tomato Plants
If the plant canopy becomes too thick, prune some of the leaves. Opening up the plant improves air circulation, which helps prevent disease and lets the fruit ripen well.
Tomato Growing FAQ
How long do tomato seeds take to germinate?
Tomato seeds usually sprout in 7–10 days when the soil is kept moist and warm.
How deep should I plant tomato seeds?
Plant them about 1/8 inch deep, just barely covered with soil.
How far apart should tomato plants be?
Space tomato plants about 24 inches apart.
What’s the difference between determinate and indeterminate tomatoes?
Determinate tomatoes grow to a set height and ripen their fruit over a few weeks. Indeterminate tomatoes keep growing and producing until frost, so they need a trellis or tall support.
Can tomatoes survive frost?
No. Tomatoes aren’t frost hardy, so wait until after your last frost to plant them outdoors.
Why are my tomato seedlings leggy?
Leggy, stretched seedlings usually aren’t getting enough light. Move them closer to a grow light or into a brighter spot.