Zone 7 tomatoes: an April start and a long, hot season

The real enemy for zone 7 tomatoes is July, not frost. Plant them out from mid-April to mid-May, and they’ll set a good crop of fruit before the worst heat arrives.

Zone 7’s last frost is usually around early April and the first fall frost comes around the end of October. That’s a long season, nearly seven months, and it rewards an early start.

Starting seeds

Sow indoors from early February to early March, six to eight weeks before you plan to transplant. Sow a quarter inch deep in seed-starting mix and keep the trays warm, around 70 to 80 °F, until the seedlings appear. Then give them strong light, either a sunny window that’s warm all day or a grow light a few inches above the leaves.

Pot them on into 4-inch pots when the first true leaves show, and harden them off outside for a week before planting.

When to plant out

Mid-April is the start of the window. Even after the average last frost, a cold night in mid-April is still possible, so keep row cover handy. Planting in the second half of April gives a good balance: warm enough soil for the roots to grow away, and an early start on the season.

These dates are a guide, not a rule. Zones are mapped by winter lows, not frost dates. Gardens on high ground or in frost pockets can be a couple of weeks later, and cities and coastal areas are often earlier.

Planting

• Bury the stem so only the top third of the plant shows. Tomatoes grow roots from the buried stem.
• Space plants 18 inches apart in rows 2 feet apart.
• Stake or cage them at planting time. Indeterminate varieties reach 6 feet or more over a long zone 7 season.
• Water well and mulch with straw or shredded leaves to keep the soil cool and evenly moist through the summer.

Basil, marigolds, carrots, parsley and garlic make good neighbours. Keep tomatoes apart from potatoes and sweet corn.

Getting through the heat

Tomato flowers don’t set fruit well when days are above about 90 °F or nights stay above about 75 °F. In a hot zone 7 summer, plants can flower for weeks in July and August and give almost nothing. They aren’t sick. They’re waiting for cooler nights.

A few things help:

1. Plant early. Plants set out in April have most of their main crop set by early July.
2. Choose varieties that cope with heat. Cherry tomatoes and many paste tomatoes keep setting fruit when large beefsteaks stop. Seed catalogs often mark heat-tolerant varieties.
3. Water deeply, not often. A long soak twice a week in dry weather is better than a little every day. Steady moisture also prevents blossom end rot and split fruit.
4. Keep the leaves. Prune lightly. A full canopy shades the fruit and prevents sunscald.

When nights cool down in September, plants that have kept healthy often flower and set a second flush of fruit. Picking can carry on until the first frost in late October.

Picking

The first ripe fruit usually arrives in late June, 55 to 85 days after transplanting. Pick when fully colored, or when they first start to change color if birds or squirrels are a problem. They finish ripening indoors with no loss of flavor.

Common problems

Early blight and leaf spot. Brown spots on the lower leaves that spread upward, worse in humid summers. Mulch, water at the base, space plants well and remove affected leaves.

Hornworms. Big green caterpillars that strip leaves overnight. Check plants in the evening and pick them off.

Blossom end rot. Dark patches on the bottom of the fruit, caused by uneven watering. Mulch and water steadily.

For every window in one place, open the tomato page and choose zone 7 from the frost menu. There’s a separate guide for tomatoes in zone 5 if you garden further north.