Start with seeds or seedlings, not mature plants
You can grow tomatoes from seed indoors six to eight weeks before your last spring frost, or buy seedlings from a garden center and plant them directly outside after frost danger passes. Seeds take longer but cost less and give you more variety choices. Seedlings are faster—they're ready to go in the ground in three to four weeks. Either way, you're starting with something small that needs warmth, light, and consistent moisture before it produces fruit.
If you choose seeds, fill a seed tray or small pots with seed-starting mix (not garden soil—it's too dense). Plant one or two seeds per cell, about a quarter-inch deep. Keep the soil moist but not waterlogged, and place the tray in a warm spot—70 to 80 degrees Fahrenheit is ideal. Most tomato seeds sprout in five to ten days.
Key Takeaways
- Tomato seeds need warmth (70 to 80 degrees), consistent moisture, and 14 to 16 hours of light daily to grow into strong seedlings indoors.
- Transplant seedlings outdoors only after your last frost date has passed and daytime temperatures stay above 60 degrees.
- Plant seedlings deep—bury the stem up to the first true leaves—because tomatoes form roots all along the buried stem.
- Water at the soil level, not on the leaves, and provide a cage or stake for support as the plant grows.
- Most tomato varieties produce fruit 60 to 85 days after transplanting, depending on the type and your climate.
Give seedlings light and keep them from getting leggy
Once seedlings sprout, they need 14 to 16 hours of bright light daily. A sunny windowsill works if it faces south and gets unobstructed light. A grow light placed 2 to 3 inches above the seedlings is more reliable and prevents the stretching and weakness that happens when seedlings reach for distant light. Adjust the light higher as the seedlings grow.
Keep the soil moist but not soggy—water from below if possible by setting the tray in a shallow pan of water for 10 to 15 minutes, then remove it and let it drain. Overwatering causes damping off, a fungal disease that kills seedlings at the soil line. Once seedlings have two sets of true leaves (the second set looks like actual tomato leaves, not the smooth seed leaves), you can thin them to one per cell or pot, or transplant the strongest one to a larger container.
Harden off seedlings before moving them outside
Hardening off means gradually exposing indoor seedlings to outdoor conditions so they don't wilt or die from the shock. Start about a week before your last frost date. Place seedlings outside in a sheltered, shaded spot for one to two hours on the first day. Each day, increase the time outside and gradually move them into more sunlight. By day seven or eight, they should handle a full day of outdoor sun and wind.
Watch the weather forecast during this period. If frost is predicted, bring seedlings back inside. If a cold snap hits while they're hardening off, cover them with a frost cloth or move them to shelter. This process takes patience, but it's the difference between seedlings that thrive and ones that struggle for weeks after planting.
Plant seedlings deep and space them correctly
Transplant seedlings into the garden after your last frost date, when soil temperature is at least 60 degrees Fahrenheit and daytime air temperature stays above 60 degrees. Tomatoes planted in cold soil sit dormant and are more prone to disease. Choose a spot that gets at least six to eight hours of direct sun daily—more is better.
Dig a hole slightly deeper than the seedling's root ball and bury the stem up to the first set of true leaves. Tomatoes form roots all along the buried stem, which creates a stronger root system. Space plants 24 to 36 inches apart, depending on the variety—determinate (bush) types need less space, indeterminate (vining) types need more. Gently firm soil around the base and water thoroughly.
Water consistently and support the growing plant
Tomatoes need one to two inches of water per week, delivered as evenly as possible. Water deeply at the soil level early in the morning, not on the leaves—wet foliage invites fungal disease. If you use a soaker hose or drip line, water runs straight to the roots and stays off the plant. In hot weather, you may need to water every two to three days. In cooler weather with rain, you may skip a week. The goal is soil that stays moist but not waterlogged.
Install a cage or stake when you plant the seedling, not later—driving a stake through roots damages them. Determinate varieties often need only a cage. Indeterminate varieties grow tall and benefit from a stake or string support tied loosely around the stem as it grows. Prune suckers (shoots that grow between the main stem and branches) on indeterminate varieties to direct energy into fruit production, but leave them on determinate types.
Fertilize every two to three weeks once flowering starts
Tomatoes don't need heavy feeding, but they do need consistent nutrients. If your soil is poor, work compost or balanced fertilizer into the planting hole before transplanting. Once the plant flowers, feed every two to three weeks with a fertilizer balanced for fruiting—something like 5-10-10 or 10-10-10 works well. Follow the package directions for amount based on plant size.
Too much nitrogen (the first number) produces lots of leaves but few flowers and fruit. Too little phosphorus and potassium (the second and third numbers) results in slow growth and poor fruiting. If leaves yellow while veins stay green, the plant may need magnesium—dissolve one tablespoon of Epsom salt in a gallon of water and pour it around the base.
Harvest fruit when it reaches full color
Most tomato varieties produce fruit 60 to 85 days after transplanting. Fruit is ready to pick when it reaches full color for its variety—deep red, orange, yellow, or pink depending on the type. Gently twist and pull, or use pruning shears to cut the stem. Tomatoes continue to ripen after picking if kept at room temperature out of direct sun.
If frost is forecast before all fruit ripens, pick all remaining tomatoes—even green ones—and place them in a cardboard box with a ripe banana or apple, which releases ethylene gas and speeds ripening. Store ripe tomatoes at room temperature, not in the refrigerator, which damages flavor and texture. A single plant can produce 10 to 30 pounds of fruit over a season, depending on variety and growing conditions.
Frequently Asked Questions
What's the difference between determinate and indeterminate tomatoes?
Determinate varieties grow to a fixed size, flower all at once, and produce most of their fruit in a short window—good for canning. Indeterminate varieties grow continuously, flower and fruit all season, and keep producing until frost. Check the seed packet or plant label to know which you have.
Why are my tomato flowers dropping without making fruit?
Flowers drop when temperatures fall below 55 degrees at night or above 90 degrees during the day, when the plant is stressed by inconsistent watering, or when nitrogen is too high. Keep soil evenly moist, avoid over-fertilizing, and be patient—once temperatures stabilize, flowering and fruiting resume.
Can I grow tomatoes in a pot instead of the ground?
Yes. Use a pot at least 18 to 20 inches deep and wide, fill it with quality potting soil, and water more often than in-ground plants because pots dry faster. Determinate varieties work better in containers than indeterminate types, which need more root space.
What should I do if I see brown spots on leaves?
Brown spots with concentric rings usually mean early blight or septoria leaf spot, both fungal diseases. Remove affected leaves, improve air circulation by pruning lower branches, water only at soil level, and avoid working in the plant when it's wet. Fungicide sprays slow the disease but don't stop it once it starts.
How do I know when to stop watering before frost?
Stop watering about two weeks before your first expected frost date. This slows growth and encourages the plant to ripen remaining fruit rather than produce new growth. Pick all fruit before the first hard frost, when temperatures drop below 28 degrees.