Start tomatoes indoors 6 to 8 weeks before your last spring frost

The fastest way to get tomatoes is to buy transplants from a garden center in spring, but growing from seed gives you more varieties and costs less. Start seeds indoors under grow lights or on a sunny windowsill 6 to 8 weeks before the date of your region's last frost. You can find your frost date by searching "[your city] last frost date" — it varies by hundreds of miles.

Fill a seed tray or small pots with seed-starting mix (not garden soil, which compacts). Plant seeds about a quarter-inch deep, keep the soil moist but not waterlogged, and maintain a temperature between 70 and 80 degrees Fahrenheit. Seeds sprout in 5 to 10 days under those conditions. Once seedlings have their first true leaves — the second set that appears — move them to individual pots so roots have room to grow.

Water from below by setting pots in a tray of water for 10 minutes rather than pouring from above, which can topple fragile stems. Provide 14 to 16 hours of light daily. If seedlings look pale or stretched, they need stronger light or to be moved closer to the bulb.

Key Takeaways

  • Seeds started indoors 6 to 8 weeks before your last frost date will be ready to transplant when soil warms in spring.
  • Tomatoes need full sun (at least 6 to 8 hours daily), rich soil with compost mixed in, and consistent water — not soggy, not dry.
  • Pinch off the lowest leaves once plants are in the ground to prevent soil-borne disease and encourage stronger root growth.
  • Most varieties need a cage or stake for support, installed at planting time to avoid damaging roots later.
  • Harvest when fruit is fully colored but still slightly soft; tomatoes ripen faster off the vine in a paper bag at room temperature.

Harden off seedlings before moving them outside

Hardening off means gradually exposing indoor seedlings to outdoor conditions so they don't wilt or sunburn when transplanted. Start 7 to 10 days before your planned planting date. Place seedlings outdoors in a sheltered, shaded spot for 1 to 2 hours, then bring them back inside. Each day, increase the time outside and move them into more direct sun, until they spend a full day and night outdoors.

Watch the weather forecast during this period. If frost is predicted, bring seedlings inside. If a cold snap arrives unexpectedly after transplanting, cover plants with a sheet or row cover overnight.

Plant tomatoes in warm soil with full sun and rich compost

Transplant seedlings into the garden once soil temperature reaches 60 degrees Fahrenheit and nighttime lows stay above 50 degrees. Tomatoes grow best in soil that has been amended with 2 to 3 inches of compost worked into the top 8 to 10 inches. They need at least 6 to 8 hours of direct sun daily — more is better.

Dig a hole slightly deeper than the root ball and bury the stem up to the lowest leaves. Tomato stems can develop roots all along their buried length, which strengthens the plant. Space plants 24 to 36 inches apart depending on variety — check the seed packet or transplant label for the mature size.

Install a cage or stake at planting time. Trying to add support later risks damaging roots. Water deeply after planting and keep soil consistently moist — about 1 to 1.5 inches per week from rain or irrigation. Mulch around the base with 2 to 3 inches of straw or shredded leaves to retain moisture and keep soil temperature steady.

Remove lower leaves and watch for common pests and diseases

Once plants are established, pinch off leaves that touch the soil or hang below the lowest fruit cluster. These lower leaves are most vulnerable to fungal diseases like early blight and septoria leaf spot, which spread from soil splash. Removing them improves air circulation and prevents infection from taking hold.

Check plants weekly for pests. Hornworms are large green caterpillars that can strip a plant in days — pick them off by hand or spray with spinosad if infestation is heavy. Whiteflies cluster on leaf undersides and weaken plants; a strong spray of water or neem oil controls them. Spider mites cause yellowing and fine webbing, especially in hot, dry weather; increase watering and humidity to discourage them.

If you see brown spots with concentric rings on lower leaves, that is early blight. Remove affected leaves when ready and dispose of them (not in compost). Improve air flow by pruning lower branches and spacing plants farther apart if needed. Water at the soil level, not overhead, to keep foliage dry.

Prune suckers on indeterminate varieties to direct energy to fruit

Indeterminate tomatoes grow as a single tall vine all season and produce fruit continuously until frost. Determinate varieties grow as a bush, produce most fruit at once, and stop growing. Check your seed packet or label to know which type you have.

On indeterminate plants, remove suckers — the shoots that grow between the main stem and branches. Suckers don't produce fruit and drain energy from the main plant. Pinch them off when they are small, between your thumb and finger. Leave the main stem and the branches that produce flowers and fruit.

Determinate varieties need little to no pruning. Removing leaves from either type during the growing season is unnecessary and stresses the plant — let it keep its foliage to power fruit development.

Harvest tomatoes when fully colored and slightly soft

Pick tomatoes when they are fully colored but still have a slight give when you squeeze gently. Fruit picked at this stage continues to ripen off the vine and develops better flavor than tomatoes picked hard and green. Twist gently or use pruners to avoid damaging the stem.

If frost is forecast before the end of the season, pick all remaining fruit — even green ones. Place them in a paper bag or cardboard box at room temperature (around 68 to 72 degrees Fahrenheit) in a dark spot. They will ripen over 1 to 3 weeks. Tomatoes ripen faster in the dark than in light, and ethylene gas they produce naturally speeds ripening when fruit is enclosed.

Store ripe tomatoes at room temperature, not in the refrigerator. Cold breaks down flavor compounds and makes the texture mealy. Use them within a few days of ripening for best taste.

Frequently Asked Questions

Why are my tomato flowers dropping without setting fruit?

Flowers drop when temperatures drop below 55 degrees at night or exceed 90 degrees during the day, when soil is too dry, or when plants are overfertilized with nitrogen. Keep soil consistently moist, avoid high-nitrogen fertilizer, and be patient — once temperatures stabilize, flowering and fruit set resume.

Can I grow tomatoes in a pot?

Yes. Use a container at least 5 gallons for determinate varieties and 10 gallons for indeterminate types. Fill with potting mix (not garden soil), provide full sun, and water daily or twice daily in hot weather since containers dry out fast. Stake or cage the plant for support.

What causes blossom end rot, the dark sunken spot on the bottom of fruit?

Blossom end rot is caused by calcium deficiency, usually from inconsistent watering. Keep soil evenly moist — not soggy, not dry. Mulch to regulate moisture. Affected fruit cannot be saved, but consistent watering prevents it on new fruit forming higher on the plant.

Do I need to fertilize tomatoes?

If soil was amended with compost at planting, tomatoes usually don't need extra fertilizer the first month. After fruit sets, a balanced fertilizer (like 5-5-5) or one slightly higher in phosphorus and potassium (like 5-10-10) supports fruiting. Follow package directions and avoid excess nitrogen, which promotes leaves at the expense of fruit.

When should I stop pruning and fertilizing in late summer?

Stop pruning indeterminate plants about 4 to 6 weeks before your first expected frost date. This lets the plant focus energy on ripening existing fruit rather than growing new branches. You can continue light fertilizing, but reduce nitrogen to encourage ripening over new growth.