Plant tomatoes after your last frost date, in soil that drains well and gets at least six to eight hours of direct sun each day

Tomatoes need warmth to grow. Planting them too early — before the soil has warmed and frost danger has passed — will stall them or kill them. Check your local frost date with your county extension office or a frost date calculator online. In most of the United States, that falls between mid-April and late May, depending on where you live.

Once frost danger is gone, dig a hole slightly deeper than the root ball of your seedling. Tomatoes can be planted deeper than they were growing in their pot — they will develop roots along the buried stem, which makes them stronger. Space plants 24 to 36 inches apart so air can move between them and reduce disease.

The soil should hold moisture but not stay soggy. If your garden soil is heavy clay, mix in compost or aged manure to improve drainage. Tomatoes in containers need potting soil, not garden soil, and a pot at least 5 gallons for determinate (bush) varieties and 10 gallons for indeterminate (vining) types.

Key Takeaways

  • Wait until after your last frost date to plant, when soil temperature is at least 60 degrees Fahrenheit and ideally closer to 70.
  • Choose a spot with six to eight hours of direct sun daily, and space plants 24 to 36 inches apart to allow air circulation.
  • Plant seedlings deeper than they grew in their pot so roots develop along the buried stem and anchor the plant better.
  • Use well-draining soil amended with compost, or use potting soil for containers, and water deeply after planting.
  • Indeterminate varieties need sturdy cages or stakes installed at planting time to avoid damaging roots later.

Hardening off seedlings before planting outdoors

If you started tomatoes from seed indoors, they need to adjust to outdoor conditions before you plant them in the ground. This process, called hardening off, takes about 7 to 10 days. Start by placing seedlings outside in a sheltered, shaded spot for an hour or two, then bring them back inside.

Each day, leave them out a little longer and gradually move them into more direct light. By the end of the week, they should be able to spend a full day and night outside. This toughens the leaves and stems so they do not wilt or burn when you plant them permanently.

Preparing the planting hole and soil depth

Dig a hole about twice as wide as the root ball and slightly deeper. If your seedling is leggy or tall, you can bury it up to the first true leaves — tomatoes will root all along the buried stem. This gives the plant a stronger foundation and helps it access water deeper in the soil.

Gently loosen the roots of the seedling before placing it in the hole. If roots are circling tightly around the root ball, tease them apart with your fingers so they spread into the surrounding soil instead of continuing to circle. Backfill the hole and press the soil gently but firmly around the base.

Water thoroughly after planting so the soil settles and makes contact with the roots. The soil should be moist but not waterlogged — if water pools on the surface, your drainage needs improvement.

Staking and caging at planting time

Install stakes or cages at planting time, not later. Pushing a stake into the ground weeks after planting can damage roots and set the plant back. Determinate varieties (bush types that grow to a fixed height) usually need a cage or short stake. Indeterminate varieties (vining types that grow all season) need a sturdy cage, stake, or string support system.

A cage should be at least 5 feet tall for indeterminate types and made of sturdy material — thin wire cages often collapse under the weight of fruit and foliage. Stakes should be at least 6 feet long and driven 12 inches into the ground for stability. Tie the main stem loosely to the stake with soft material like cloth strips or garden twine, leaving room for the stem to grow.

Spacing and sunlight requirements

Space plants 24 to 36 inches apart in rows that are 3 to 4 feet apart. Crowded plants do not get enough air circulation, which leads to fungal diseases like early blight and powdery mildew. Good air flow also helps leaves dry faster after rain or watering.

Tomatoes need at least six to eight hours of direct sun daily to produce fruit and develop flavor. Less sun means fewer flowers and smaller, less sweet fruit. If your garden gets afternoon shade, plant tomatoes where they catch morning and midday sun.

Container planting and pot size

Containers must drain freely through holes in the bottom. Use potting soil, not garden soil, because potting soil is lighter and drains better. A 5-gallon pot is the minimum for determinate varieties, but 10 gallons is better. Indeterminate varieties need at least 10 gallons, and 20 gallons is ideal if you have the space.

Fill the pot with moist potting soil before planting. Plant the seedling at the same depth as you would in the ground — deeper if the seedling is tall. Place the pot in a location that gets six to eight hours of direct sun. Container plants dry out faster than in-ground plants, so check soil moisture daily once temperatures warm up.

Watering and mulching after planting

Water deeply after planting so the soil is moist 6 to 8 inches down. For the first week or two, water every two or three days if there is no rain, depending on how warm it is. Once plants are established and growing, water deeply once or twice a week rather than frequent shallow watering — deep watering encourages roots to grow deeper and makes plants more drought-tolerant.

explore 2 to 3 inches of mulch around the base of each plant, keeping it a few inches away from the stem. Mulch keeps soil temperature even, reduces water loss, and prevents soil from splashing onto lower leaves (which spreads disease). Use straw, shredded leaves, or wood chips — avoid fresh grass clippings, which can mat down and hold too much moisture.

Frequently Asked Questions

Can I plant tomatoes in the same spot every year?

No. Tomatoes are susceptible to soil-borne diseases that build up over time, especially early blight and fusarium wilt. Rotate tomatoes to a different bed each year, or at minimum wait three years before planting tomatoes in the same spot again. If you use containers, replace the potting soil each season rather than reusing it.

What if my seedlings are very tall and spindly?

Bury them deeper than normal — up to the first set of true leaves. The buried stem will develop roots and create a stronger plant. Tall seedlings usually mean they did not get enough light indoors. For next year, place seedlings under grow lights or in a very sunny window, and run a small fan nearby to strengthen the stems.

How deep should the soil be for container tomatoes?

At least 12 inches deep for determinate varieties and 18 to 24 inches for indeterminate types. Deeper containers hold more soil, which means more water and nutrients available to the plant, and the soil stays cooler in hot weather. A 10-gallon pot is roughly 12 inches deep and works well for most home gardeners.

Should I remove leaves from the seedling before planting?

No. Leave all healthy leaves on the seedling. If you are burying the stem deep, you can remove the lowest leaves so they do not sit in the soil, but keep the rest. The leaves feed the plant while it recovers from transplanting and establishes new roots.

What temperature should the soil be before planting?

At least 60 degrees Fahrenheit, but ideally 70 degrees or warmer. Cold soil slows root growth and can cause seedlings to sit and sulk for weeks. Use a soil thermometer to check — do not guess based on air temperature. Soil warms more slowly than air, especially in spring.