Plant tomatoes in spring after the last frost, in a spot that gets at least six to eight hours of direct sun each day

The timing and location matter more than most gardeners realize. Tomatoes are warm-season plants—they will not grow in cold soil and will sit dormant or rot if you plant them too early. Wait until nighttime temperatures stay above 50°F consistently, which varies by region but is typically four to six weeks after your area's last spring frost date. You can find your local frost date through your county extension office or by searching "[your state] frost date map."

Sun is equally critical. Tomatoes need at least six to eight hours of direct sunlight daily to develop flavor and ripen properly. Less sun produces weak plants with fewer fruits. Choose a spot that faces south or southwest if you are in the Northern Hemisphere, and avoid planting near trees or structures that cast afternoon shade.

Key Takeaways

  • Plant tomatoes only after your area's last frost date and when soil temperature reaches 60°F or higher, which you can check with a soil thermometer.
  • Dig a hole deeper than the root ball and bury the stem up to the first true leaves, because tomatoes will grow roots all along the buried stem for a stronger plant.
  • Space plants 24 to 36 inches apart depending on variety, and stake or cage them at planting time rather than waiting until they flop over.
  • Water deeply at the soil level once or twice weekly rather than daily shallow watering, which prevents disease and encourages deep root growth.
  • Harden off seedlings by gradually exposing them to outdoor conditions for 7 to 10 days before planting, or they will wilt and stop growing.

Prepare the soil before you dig the planting hole

Tomatoes are heavy feeders and need soil rich in organic matter and nutrients. Work compost, aged manure, or peat moss into the top 8 to 12 inches of soil before planting. If your soil is clay-heavy and drains poorly, add compost to improve drainage—tomatoes in waterlogged soil develop root rot and fungal disease.

Test your soil pH if possible. Tomatoes prefer slightly acidic soil between 6.0 and 6.8. If you do not know your soil pH, your county extension office can test a sample for a small fee, or you can buy an inexpensive soil pH kit at a garden center. If your soil is too alkaline, work in sulfur; if too acidic, add lime. These amendments take weeks to shift pH, so amend in fall if you are planning a spring garden.

Bury the stem deeper than the root ball to build a stronger root system

This is the single most important planting technique for tomatoes. Dig a hole deeper than the container your seedling came in—typically 6 to 8 inches deeper. Remove the lower leaves from the seedling, then plant it so that only the top few leaves are above soil level. The buried stem will develop roots all along its length, creating a much larger root system that anchors the plant and absorbs more water and nutrients.

If your seedling is leggy or tall, you can plant it at an angle in a shallow trench rather than straight down. The stem will straighten as it grows, and the same root development will occur. This technique is especially useful for seedlings that became too tall indoors before transplanting.

Space plants correctly and install support at planting time

Spacing depends on the variety. Determinate (bush) tomatoes need 24 inches between plants; indeterminate (vining) varieties need 30 to 36 inches. Crowded plants do not get enough air circulation, which leads to fungal disease like early blight and powdery mildew. If you are planting in rows, space rows 36 to 48 inches apart so you can walk between them and harvest without brushing wet foliage.

Install a stake, cage, or trellis at planting time, not later. Waiting until the plant is large and heavy damages roots when you drive a stake into the ground. A 5 to 6-foot stake works for indeterminate varieties; a cage 4 to 5 feet tall works for determinate types. Tie the stem loosely to the stake with soft twine or cloth strips—tight ties cut into the stem as it grows.

Water deeply and consistently, not daily and shallow

Water once or twice per week, explore water directly to the soil at the base of the plant rather than overhead. Wet foliage invites fungal disease. Each watering should be deep enough to moisten the soil 6 to 8 inches down, which you can check by pushing a finger into the soil after watering. In hot weather or sandy soil, you may need to water twice weekly; in cool weather or clay soil, once weekly may be enough.

Inconsistent watering causes problems. Alternating between dry and wet soil leads to blossom-end rot (a dark sunken spot on the bottom of the fruit) and fruit cracking. Mulch around the base with 2 to 3 inches of straw or shredded leaves to keep soil moisture steady and reduce the need for frequent watering.

Harden off seedlings before planting them outside

If you started seedlings indoors under lights, they are not ready for outdoor sun and wind. Hardening off means gradually exposing them to outdoor conditions over 7 to 10 days. Start by placing seedlings in a sheltered, shaded spot outdoors for an hour or two, then bring them back inside. Each day, increase the time outside and gradually move them into more sun. By day 7 or 10, they should be in full sun for the entire day and ready to plant.

Seedlings that go from a warm, still indoor environment directly into outdoor sun and wind will wilt, stop growing, and may not recover. The hardening-off period is not optional—it is the difference between a plant that thrives and one that struggles all season.

Frequently Asked Questions

Can I plant tomatoes in containers instead of the ground?

Yes. Use a container at least 5 gallons for determinate varieties and 10 gallons for indeterminate types. Fill it with potting mix (not garden soil), and follow the same deep-planting and watering rules. Containers dry out faster than ground soil, so check moisture every few days and water when the top inch feels dry.

What if my seedlings are already tall and leggy when it is time to plant?

Plant them deeper than usual, burying more of the stem. You can also plant them at a 45-degree angle in a shallow trench—the stem will straighten as it grows and will develop roots along the buried portion. Both methods work; choose whichever fits your garden layout.

How do I know if my soil is warm enough to plant?

Soil should be 60°F or warmer. You can check with a soil thermometer, which costs a few dollars at a garden center. Push it 4 inches into the soil in the morning. If you do not have a thermometer, wait until nighttime temperatures stay above 50°F for at least a week—soil will have warmed by then.

Should I fertilize when I plant, or wait until the plant is growing?

If you worked compost or aged manure into the soil before planting, you do not need to fertilize at planting time. Once the plant flowers, you can feed every two to three weeks with a balanced fertilizer or one slightly higher in phosphorus to encourage fruit production. Avoid high-nitrogen fertilizer, which produces lots of leaves but few tomatoes.