Plant seedlings after the last frost date in your area, when soil temperature reaches 60°F
Tomato seedlings go in the ground when two conditions are met: the date of your area's last spring frost has passed, and soil temperature is at least 60°F. You can find your last frost date by entering your zip code into the USDA Hardiness Zone map or asking your local cooperative extension office. Soil temperature matters more than air temperature — a soil thermometer costs under $10 and takes the guesswork out.
Planting too early kills seedlings. Soil below 60°F slows root growth and invites fungal disease. If you have seedlings ready but soil is still cold, keep them in pots indoors under grow lights or in a sunny window for another week or two. They will not suffer from waiting.
Key Takeaways
- Wait until soil temperature reaches 60°F and your area's last frost date has passed before moving seedlings outdoors.
- Choose a spot that gets at least six to eight hours of direct sun each day, because tomatoes need full sun to produce fruit.
- Dig a hole deeper than the seedling's root ball and bury the stem up to the first true leaves, since tomatoes will grow roots all along the buried stem.
- Space plants 24 to 36 inches apart so air can move between them and reduce disease.
- Water deeply after planting and keep soil consistently moist but not waterlogged for the first two weeks while roots establish.
Choose a location with at least six to eight hours of direct sun
Tomatoes need full sun to produce fruit. A spot that gets six hours is the bare minimum; eight to ten hours is better. Morning sun is especially valuable because it dries dew off the leaves and reduces fungal disease. Avoid planting in shade cast by trees, fences, or buildings, because shaded plants produce fewer tomatoes and ripen them more slowly.
If your yard has limited sun, grow tomatoes in containers on a patio or deck where you can position them in the sunniest spot. A 5-gallon bucket or larger pot works well and gives you control over soil quality and moisture.
Prepare soil with compost and check drainage before planting
Tomatoes grow best in soil rich in organic matter. Mix 2 to 3 inches of finished compost into the top 8 to 10 inches of soil where you will plant. If you do not have compost, aged manure or a bagged soil amendment work. This feeds the plant and improves the soil's ability to hold moisture without becoming waterlogged.
Check drainage by digging a hole 12 inches deep, filling it with water, and watching how fast it drains. If water is still there after two hours, the soil drains too slowly and tomatoes will rot. In that case, either amend heavily with compost and sand, or plant in a raised bed or container instead.
Dig the hole deeper than the root ball and bury the stem
Tomatoes have a useful trait: they grow roots all along their buried stem. Dig a hole deeper than the seedling's root ball — if the seedling is 6 inches tall, dig 8 to 10 inches deep. Remove the lower leaves from the seedling so they will not be buried, then plant it so the remaining stem is covered up to the first set of true leaves. The buried stem will develop roots, creating a stronger root system.
Gently firm soil around the seedling with your hands. Do not pack it hard; you want soil in contact with the stem but still loose enough for roots to push through. If the seedling is leggy or tall, you can even plant it at an angle — it will straighten up as it grows.
Space plants 24 to 36 inches apart to allow air circulation
Crowded tomatoes develop disease because leaves stay wet and air cannot move between plants. Space determinate varieties (bush types) 24 inches apart and indeterminate varieties (vining types) 30 to 36 inches apart. Check the seed packet or plant label for the mature size of your variety.
Spacing also makes it easier to harvest, prune, and tie up vining plants as they grow. If you are planting in rows, space rows 36 to 48 inches apart so you can walk between them without brushing wet foliage.
Water deeply after planting and maintain consistent moisture
Water the seedling thoroughly right after planting so soil settles around the roots and removes air pockets. For the first two weeks, keep soil consistently moist — not soggy, but not dry either. Check soil 2 inches down with your finger; if it feels dry, water. Once the plant is established and growing, water deeply once or twice a week depending on heat and rainfall, aiming for about 1 to 2 inches per week.
Water at the base of the plant, not on the leaves. Wet foliage invites fungal disease like early blight and septoria leaf spot. Drip irrigation or soaker hoses deliver water directly to the soil and are worth the small investment if you grow tomatoes every year.
Install support stakes or cages early to avoid damaging roots later
Install a stake, cage, or trellis at planting time rather than waiting until the plant is large. Driving a stake into the ground later risks piercing roots and damaging the plant. A 5 to 6-foot stake works for indeterminate varieties; a 3 to 4-foot cage suits determinate types. Tie the stem loosely to the support with soft twine or cloth strips as it grows, leaving room for the stem to expand.
Proper support keeps fruit off the ground where it can rot or be eaten by slugs and insects, improves air circulation, and makes harvesting easier. It also prevents the plant from breaking under the weight of ripe fruit.
Frequently Asked Questions
Can I plant tomatoes in the same spot every year?
No. Tomatoes and their relatives (peppers, eggplant, potatoes) are susceptible to soil-borne diseases that build up over time. Rotate tomatoes to a different bed or area of the garden each year, or plant them at least 3 feet away from where they grew the previous season. If you must reuse the same spot, replace the top 6 inches of soil with fresh compost.
What if my seedling is very tall and spindly?
Bury it deeper than normal, even at an angle if needed. The buried stem will develop roots and create a stronger plant. Tall seedlings usually result from insufficient light indoors; next year, use grow lights positioned 2 to 3 inches above seedlings and run them 14 to 16 hours daily.
How long before I see flowers and fruit?
Most tomato varieties flower 4 to 6 weeks after transplanting and produce ripe fruit 6 to 8 weeks after that, depending on variety and temperature. Cooler weather slows flowering and ripening. Consistent warmth, sun, and water speed up the process.
Should I fertilize when I plant?
If you mixed compost into the soil, you do not need to fertilize at planting. Once the plant flowers, you can feed it every two to three weeks with a balanced fertilizer or one slightly higher in phosphorus to encourage fruit. Avoid high-nitrogen fertilizer, which produces lots of leaves but few tomatoes.