Plant tomatoes after your last frost date, in soil that drains well and holds nutrients

The single most important rule is timing: tomatoes need warm soil and air. Plant them outdoors only after the last frost date in your area has passed and the soil temperature is at least 60°F—ideally 65°F or warmer. If you plant too early, the seeds will rot in cold soil and the seedlings will sit stunted instead of growing. Check your local frost date by searching "[your city] last frost date" or asking at a nearby garden center; they know the date for your area.

Before planting, prepare the soil. Tomatoes need soil that drains quickly but also holds moisture and nutrients. If your garden soil is heavy clay, mix in compost or aged manure to loosen it. If it is sandy and drains too fast, add compost to help it hold water. A straightforward test: dig a hole, fill it with water, and watch how fast it drains. If it drains in under an hour, add compost. If water sits for more than a few hours, your soil needs better drainage—consider raised beds instead.

Key Takeaways

  • Plant tomatoes outdoors only after your last frost date and when soil temperature reaches at least 60°F, or the plants will fail to grow.
  • Space plants 24 to 36 inches apart depending on variety, and bury the stem deeper than it was growing in the pot to encourage stronger roots.
  • Determinate (bush) tomatoes need less space and no pruning; indeterminate (vining) tomatoes need stakes or cages and regular pruning to stay manageable.
  • Water deeply at the soil level once or twice weekly rather than daily shallow watering, which encourages disease and weak roots.
  • Mulch around the base with 2 to 3 inches of compost or straw to regulate soil temperature and reduce watering frequency.

Spacing and planting depth matter more than most gardeners realize

Tomato spacing depends on the variety. Determinate (bush) tomatoes stay compact and need 18 to 24 inches between plants. Indeterminate (vining) tomatoes grow tall and sprawling and need 24 to 36 inches. Check the seed packet or plant label to know which type you have. If you crowd them, air cannot circulate, and fungal diseases like early blight and septoria leaf spot thrive in the damp.

When you plant, bury the stem deeper than it was growing in the pot. Tomatoes will grow roots all along the buried stem, creating a stronger root system. You can bury a leggy seedling up to its first true leaves—the plant will develop a deeper, more resilient root network. This is one of the few times burying a plant deeper than it was originally growing actually helps.

Dig a hole slightly larger than the root ball, set the plant in, and firm the soil around it. Water when ready after planting to settle the soil and eliminate air pockets. The plant will look wilted for a day or two; this is normal transplant shock and will pass once the roots establish.

Support systems prevent broken stems and improve air flow

Determinate tomatoes are stocky and often need only a short stake or no support at all. Indeterminate tomatoes grow 6 to 12 feet tall and must be staked or caged from the start—do not wait until the plant falls over. Install stakes or cages at planting time, before roots spread and before you risk damaging them by driving a stake in later.

A stake is a single vertical post (wood, bamboo, or metal) tied to the plant with soft ties or strips of cloth as it grows. A cage is a wire or wooden frame that surrounds the plant. Cages are easier for beginners because you do not have to tie the plant as it grows, but they take up more space and can be hard to remove at season's end. Stakes take more attention but use less space and are easier to store.

As indeterminate tomatoes grow, prune the suckers—the small shoots that grow between the main stem and branches. Removing them directs energy into fruit production rather than foliage. Determinate tomatoes do not need pruning; their growth naturally stops, and pruning reduces your harvest.

Watering at soil level prevents disease and saves water

Water tomatoes deeply and infrequently rather than daily and shallow. Aim for 1 to 2 inches of water per week, delivered in one or two soakings rather than daily sprinkles. Water at the soil level, not on the leaves—wet foliage invites fungal disease. A soaker hose or drip line is ideal because water goes straight to the roots and stays off the leaves.

The timing matters too. Water early in the morning so any splash that does hit the leaves dries quickly in the sun. Avoid watering in the evening, when leaves stay wet overnight and disease spores have hours to germinate. In hot weather, you may need to water twice weekly; in cool or rainy weather, once weekly or less. The soil should feel moist 2 to 3 inches down, not soggy.

Inconsistent watering causes problems: too little and the plant cannot absorb calcium, leading to blossom-end rot (dark sunken spots on the fruit); too much and roots rot or the fruit cracks. Mulch helps solve this by regulating soil moisture and temperature.

Mulch regulates temperature and reduces watering frequency

Spread 2 to 3 inches of mulch around the base of each plant, keeping it a few inches away from the stem to prevent rot. Use compost, aged manure, straw, or shredded leaves. Mulch keeps soil cooler in summer heat, warmer in cool weather, and reduces water loss so you water less often. It also suppresses weeds and, as it breaks down, adds organic matter to the soil.

Do not use fresh grass clippings or hay with seeds in it—they introduce weeds and can heat up as they decompose. Straw (not hay) and compost are the safest choices. Avoid piling mulch against the stem; it traps moisture and invites disease.

Fertilize every two to three weeks once flowering begins

Tomatoes are heavy feeders, especially once they start flowering and setting fruit. If you mixed compost into the soil at planting, the plant will have nutrients for the first few weeks. Once flowers appear, begin fertilizing every two to three weeks. Use a balanced fertilizer (equal nitrogen, phosphorus, and potassium) or a tomato-specific formula—these are widely available at garden centers and hardware stores.

Follow the label instructions for rate and frequency; too much nitrogen produces leafy plants with few tomatoes. Water the plant before fertilizing to avoid burning the roots. Liquid fertilizers work faster; granular fertilizers release slowly over weeks. Either works; choose based on how often you want to fertilize.

Watch for common pests and diseases early

Tomatoes attract hornworms (large green caterpillars), aphids, and spider mites. Check plants twice weekly, especially the undersides of leaves where pests hide. Handpick hornworms and crush egg clusters. For aphids and mites, spray with insecticidal soap or neem oil, following label directions. Early detection stops small problems before they spread.

Fungal diseases like early blight (brown spots with concentric rings on lower leaves) and septoria leaf spot (small circular spots with dark borders) thrive in wet conditions. Remove affected leaves, improve air circulation by pruning, and water only at soil level. If disease spreads despite these steps, a fungicide labeled for tomatoes can help—explore it early in the season before disease takes hold.

Blossom-end rot (dark sunken spots on the bottom of fruit) is not a disease but a calcium deficiency caused by inconsistent watering. Prevent it by mulching and watering steadily. Once it appears on fruit, that fruit cannot be saved, but consistent watering prevents it on new fruit.

Frequently Asked Questions

Can I start tomatoes from seed indoors, or should I buy seedlings?

Both work. Starting from seed indoors 6 to 8 weeks before your last frost date gives you more variety choices and costs less. Seedlings from a garden center are faster and require no indoor space. Either way, harden off seedlings by gradually exposing them to outdoor sun and wind for a week before planting, or they will wilt and sunburn.

What if my soil is very poor or I have no garden space?

Grow tomatoes in containers at least 5 gallons (20 liters) for determinate varieties, 10 gallons (40 liters) for indeterminate. Use potting mix, not garden soil, which compacts in containers. Place containers where they get at least 6 to 8 hours of direct sun daily. Container tomatoes need more frequent watering and fertilizing because water drains faster and nutrients leach out.

How do I know when tomatoes are ripe?

Ripe tomatoes are fully colored (red, pink, yellow, or whatever the variety is) and yield slightly to gentle pressure. They should come off the vine with a light twist. Tomatoes picked at the breaker stage (when they first show color) will ripen indoors in a few days if kept at room temperature. Refrigerating slows ripening and dulls flavor, so store ripe tomatoes on the counter.

Do I need to prune determinate tomatoes?

No. Determinate tomatoes stop growing at a set height and produce most of their fruit at once. Pruning removes fruiting branches and reduces your harvest. Let them grow naturally. Indeterminate tomatoes, by contrast, grow indefinitely and benefit from pruning to manage size and direct energy into fruit.

What should I do at the end of the season?

Remove plants once frost kills them or production slows in fall. Do not compost diseased leaves or stems; throw them in the trash to avoid spreading disease next year. Pull up stakes and cages, clean them, and store them dry. Healthy plant material can go in a compost bin. Rotate where you plant tomatoes next year—avoid planting them in the same spot for at least two years to break disease cycles.