When to plant tomatoes

Tomatoes are a warm-season crop that is killed by frost and stalls in cold soil, so it goes out only once the frost risk is past and the soil has warmed. Type your town to see the dates for your weather station.

The seed packet, in short

Tomato planting dates by zone

Each row uses the typical frost dates of a zone: the middle value among towns of 10,000 people or more in it. In zone 6b, for example, the typical last frost is Apr 20, so the first step for tomatoes, start seeds indoors, falls Feb 23 to Mar 9. Towns in one zone can differ by two weeks, so your own town's dates above are the better guide.

Good to know about tomatoes

• Plants set out into cold soil can stall for up to two weeks, so waiting until soil is near 60 F pays off.
• Black plastic mulch and row covers let you plant a little earlier, but cover plants on frosty nights.
• Wait to spread straw or grass mulch until the soil has warmed to about 75 F.
• Spacing depends on how you grow them: dwarf types need about 1 ft, staked plants 1.5 to 2 ft, caged or sprawling plants up to 3 ft.

How to plant tomatoes

• Choose a spot with at least 6 hours of direct sun and deep, well-drained soil; less sun means a smaller crop.
• Tomatoes like slightly acid soil, roughly pH 6.0 to 6.8. Test the soil well ahead of planting, since changing pH takes months.
• Set transplants deep so only the top few sets of leaves show. Leggy plants can be laid sideways in a shallow trench; roots form along the buried stem.
• Put supports in at planting: drive stakes about 1 ft into the ground a few inches from the stem, or use cages with openings at least 6 in. wide so you can reach the fruit.
• Give about 1 to 1.5 in. of water a week at the soil line and keep 2 to 3 in. of organic mulch around plants once the soil is warm; steady moisture means fewer cracked fruit and less blossom-end rot.

Types that change the timing

• Determinate tomatoes stop growing at a set height and ripen most of their fruit in one short stretch, which suits canning, cages and containers.
• Indeterminate tomatoes keep growing and fruiting until frost, often reaching 6 to 8 ft, so they need tall stakes or cages.
• Early varieties, many of them determinate, are the better choice where summers are short; time to first harvest ranges from about 52 to 90 days after transplanting depending on variety.

Common mistakes

• Too much nitrogen fertilizer gives big leafy vines with few fruit.
• Letting the soil swing from dry to soaked causes cracked fruit and blossom-end rot.
• Buying transplants that already carry flowers or fruit sets them back; choose stocky green plants instead.

When tomatoes are ready

• Fruit is fully colored for its variety but still firm