Start tomatoes from seed indoors six to eight weeks before your last spring frost, or buy seedlings from a nursery and plant them outside after frost danger passes

Tomatoes need warm soil and air to thrive — they won't germinate in cold ground and will sit dormant or rot if planted too early. The fastest route for most home gardeners is buying transplants (seedlings already a few inches tall) from a garden center in spring and planting them directly into the garden or containers after the last frost date for your area has passed. If you want to start from seed indoors, count backward from your frost date: a tomato seed takes 6 to 8 weeks to become a plant large enough to move outside.

You can find your last spring frost date by searching "[your city] last frost date" or checking the USDA Hardiness Zone map online. Planting before that date is the single most common reason tomato plants fail — they'll sit in cold soil for weeks, attracting disease and pests, instead of growing.

Key Takeaways

  • Tomato seeds need warmth to sprout (70 to 80 degrees Fahrenheit) and take 6 to 8 weeks to become plants ready for the garden.
  • Transplants go in the ground only after your last frost date, when soil temperature is at least 60 degrees and ideally 70 degrees or warmer.
  • Tomatoes need 6 to 8 hours of direct sun daily, well-draining soil, and consistent water — not soggy, not bone-dry.
  • Stake or cage indeterminate (vining) varieties early; determinate (bush) types need less support but still benefit from it.
  • Pinch off suckers (shoots that grow between the main stem and branches) on indeterminate plants to direct energy into fruit instead of leaves.

Starting seeds indoors or buying transplants

If you're starting from seed, fill a seed tray or small pots with seed-starting mix (a sterile, lightweight soil blend), plant one seed per cell about a quarter-inch deep, and keep the soil moist but not waterlogged. Place the tray in a warm spot — a heat mat under the tray speeds germination to 5 to 10 days, but a warm windowsill or shelf near a heat source works too. Once seedlings sprout, move them to bright light when ready (a south-facing window or grow light 2 to 3 inches above the leaves) to prevent them from becoming leggy and weak.

Water seedlings from below by setting the tray in a shallow pan of water for 10 to 15 minutes, then removing it — this keeps the soil moist without waterlogging the roots. When seedlings develop their first true leaves (the second set to appear, which look like actual tomato leaves), thin them so only the strongest plant remains per cell, or transplant each one into its own small pot. This gives roots room to grow and prevents crowding, which weakens all the seedlings.

Buying transplants skips all this work. Look for stocky, dark-green plants with thick stems and no flowers yet — flowering transplants often struggle to establish roots after planting. Avoid leggy, pale seedlings or those already in fruit, as they've used energy that should go into root development.

Hardening off seedlings and planting outside

Hardening off means gradually exposing indoor seedlings to outdoor conditions over 7 to 10 days before planting. Start by placing them in a sheltered, shaded spot outdoors for 1 to 2 hours, then bring them back inside. Each day, increase the time outside and move them into more sun. By the end of the period, they should spend a full day outside in dappled sun. This toughens the leaves and stems so they don't wilt or sunburn when planted in the garden.

Plant seedlings outside only after your last frost date and when soil temperature is at least 60 degrees (ideally 70 degrees or warmer). Dig a hole slightly deeper than the root ball, set the plant in, and bury it up to the first true leaves — tomatoes will root along the buried stem and develop a stronger base. Space plants 24 to 36 inches apart depending on variety (check the seed packet or plant label). Water thoroughly after planting and keep the soil consistently moist for the first week while roots establish.

Sunlight, soil, and watering

Tomatoes need 6 to 8 hours of direct sun daily to produce fruit and ripen it fully. Less sun means fewer tomatoes and slower ripening. Choose a spot that gets morning sun (which dries dew and reduces disease) and afternoon sun, even if it's partial shade in the hottest part of summer — in very hot climates, afternoon shade can actually help prevent sunscald on fruit.

Soil should drain well and hold some organic matter. If your garden soil is heavy clay, mix in 2 to 3 inches of compost before planting. Tomatoes prefer slightly acidic soil (pH 6.0 to 6.8), but they're forgiving — most garden soil in that range will work. In containers, use potting mix (not garden soil), which drains faster and won't compact over the season.

Water deeply and consistently — aim for 1 to 2 inches per week from rain or irrigation. Water at the base of the plant in the morning to keep leaves dry and reduce disease. Inconsistent watering (dry for days, then soaked) causes problems like blossom-end rot (dark spots on the bottom of fruit) and fruit cracking. Mulch around plants with 2 to 3 inches of straw or shredded leaves to keep soil temperature steady and reduce water loss.

Support, pruning, and feeding

Install stakes or cages early — at planting time or within a week — so you don't damage roots later. Indeterminate varieties (vining types that grow 6 feet or taller) need sturdy stakes or tall cages and benefit from pruning. Determinate varieties (bush types that stay 3 to 4 feet tall) need less support but still appreciate a cage to keep fruit off the ground and away from soil-borne disease.

On indeterminate plants, pinch off suckers — the shoots that grow in the angle between the main stem and a branch — once they're an inch or two long. This directs the plant's energy into fruit instead of extra foliage. Don't prune determinate plants; they produce all their fruit at once and need the leaves to support it.

Feed tomatoes every 2 to 3 weeks once they start flowering, using a balanced fertilizer (like 10-10-10) or one higher in phosphorus and potassium (like 5-10-10) to encourage fruiting rather than leafy growth. Follow the label rate. Overfertilizing, especially with nitrogen, produces lots of leaves and few tomatoes.

Common pests and diseases

Hornworms are large green caterpillars that can strip a plant bare. Hand-pick them or spray with Bacillus thuringiensis (Bt), a natural bacteria that kills caterpillars but is safe for people and beneficial insects. Aphids cluster on new growth and can be sprayed off with water or treated with insecticidal soap. Spider mites cause yellowing and fine webbing, especially in hot, dry weather — increase humidity by misting or watering more often.

Early blight and late blight are fungal diseases that cause brown or black spots on leaves and fruit. Early blight starts on lower leaves and moves up; late blight appears suddenly in cool, wet weather. Remove affected leaves, improve air circulation by pruning lower branches, water at the base only, and mulch to prevent soil splash. Fungicide sprays (sulfur or copper) can slow spread if caught early. Late blight is harder to control and may require stronger fungicides — ask your local extension office for current recommendations.

Harvesting and ripening

Tomatoes ripen from the inside out, so you can pick them when they show color — they'll finish ripening on the counter. Fully ripe tomatoes come off the vine with a gentle twist. Harvest regularly to encourage the plant to keep producing fruit throughout the season.

If frost is coming and you have green tomatoes still on the vine, pick them and place them in a cardboard box or paper bag with a ripe banana or apple (which release ethylene gas and speed ripening). Keep them at room temperature, out of direct sun. They'll ripen over days or weeks depending on how mature they were when picked.

Container growing for tomatoes

Tomatoes grow well in containers if the pot is large enough — at least 5 gallons for determinate varieties, 10 gallons or larger for indeterminate types. Use potting mix, not garden soil. Water containers more often than in-ground plants because they dry out faster, especially in heat. Feed every 2 weeks because watering leaches nutrients from the limited soil.

Containers can be moved to catch more sun or brought under cover if heavy rain or frost threatens. In very hot climates, moving a container to afternoon shade can prevent fruit from sunburning. Check soil moisture daily in summer — container plants may need water every day or even twice daily in extreme heat.

Frequently Asked Questions

Can I plant tomatoes in the same spot every year?

No — tomato diseases live in soil and build up over time. Rotate tomatoes to a different bed each year, or replace the top 6 inches of soil if you must plant in the same spot. Avoid planting other nightshade crops (peppers, eggplant, potatoes) in that spot the year before or after.

Why are my tomato flowers dropping without making fruit?

Flowers drop when temperatures are too cold (below 55 degrees at night), too hot (above 90 degrees during the day), or when the plant is stressed by inconsistent watering or too much nitrogen fertilizer. Wait for better weather, keep soil evenly moist, and switch to a lower-nitrogen fertilizer.

What's the difference between determinate and indeterminate tomatoes?

Determinate varieties grow as a bush, produce all their fruit in a short window, and stop growing at a set height — good for canning or sauce-making. Indeterminate varieties vine and produce fruit all season until frost, so they're better for fresh eating. Check the seed packet or plant label to know which you have.

Do I need to remove leaves from tomato plants?

On indeterminate plants, remove lower leaves (up to the first fruit cluster) once fruit sets to improve air circulation and reduce disease. Don't strip the plant bare — leaves feed the fruit. On determinate plants, leave most leaves alone.

Can I save seeds from my tomatoes?

Yes, but only from heirloom or open-pollinated varieties — seeds from hybrid tomatoes won't grow true to type. Scoop seeds and gel into a jar, add a little water, let them ferment for 2 to 3 days (this removes a germination inhibitor), rinse well, and dry on a paper plate for 2 to 3 weeks before storing in a cool, dry place.