What to plant in May

May is the primary planting month for warm-season vegetables in zones 5–7: tomatoes, peppers, beans, squash, cucumbers, corn, and basil. In zone 8–9, May means managing heat and succession planting. In zones 3–4, May is the cool-season window. Don't skip hardening off transplants

For most American gardeners in zones 5–7, May is the main planting month of the year. Last frost has passed or will pass this month, warm-season crops go in the ground, and the summer garden takes shape.

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The most important May rule

Per Penn State Extension, soil temperature matters more than calendar date. Tomatoes planted in cold soil (below 60°F) will sit and stall even if there's no frost. Beans planted below 60°F germinate poorly and rot in the ground. An inexpensive a soil thermometer is one of the most useful investments for any vegetable gardener.

Last frost dates and soil readiness for May planting:

• Zone 5 (Chicago, Denver): Last frost May 15–30. Soil reaches 60°F around May 15–20.
• Zone 6 (Philadelphia, Columbus): Last frost April 30. Soil typically hits 60°F by May 1–15.
• Zone 7 (Long Island, DC): Last frost April 1–15. Soil is usually 60°F+ by May 1.

What to plant outdoors in May

Tomatoes

In zone 7, May 1–15 is the sweet spot for tomato transplanting. The plants go into warm soil (60°F+), nights are consistently above 50°F, and the season is long enough to produce before fall frost (typically late October).

Per Penn State Extension, "transplant tomatoes on a cloudy day or late afternoon to reduce transplant stress." Bury the stem deep — to within 2–3 sets of leaves of the top growth. Per NC State Extension, "tomatoes can be planted deeper than they grew in the container" because they form roots all along the buried stem, producing a stronger root system.

Spacing: Most determinate tomatoes need 24–36 inches; indeterminate varieties need 36–48 inches. Per Penn State Extension, "crowded plants have more disease problems and lower yields."

Staking: Install cages or stakes at transplanting time, before the plants grow large enough to be disturbed. Per NC State Extension, "waiting until the plant needs support to install stakes often damages roots."

Peppers and eggplant

Plant after last frost, when soil is consistently above 60°F. Peppers are more cold-sensitive than tomatoes — per Penn State Extension, "peppers planted in soil below 65°F grow very slowly and may not set fruit." In zone 7, the first week of May is usually suitable.

Plant peppers shallowly — unlike tomatoes, they don't form adventitious roots along the stem. Per Penn State Extension, plant at the same depth as the nursery container.

Beans — the easiest May sow

Bush beans are the most straightforward May planting in zones 5–7. Per Penn State Extension, "direct sow bush beans after last frost when soil temperature reaches 60°F." Sow 1 inch deep, 3 inches apart. Germination in 7–10 days at 65–75°F. First harvest in 50–55 days.

Pole beans need a trellis — install before planting. Sow at the base of the trellis, 4 inches apart. Pole beans take slightly longer (60–65 days) but produce a longer harvest than bush beans.

Summer squash and zucchini

The fastest vegetable to produce from seed. Per NC State Extension, zucchini goes from seed to first harvest in 45–55 days. Direct sow 2–3 seeds per hill (a low mound 4–6 inches high), 1 inch deep. Thin to 1 plant per hill once seedlings establish.

One or two zucchini plants per family is typically plenty — three or more and you'll be leaving zucchini on neighbors' porches anonymously by August.

Cucumbers

Per Penn State Extension, "direct sow cucumbers after last frost when soil temperatures reach 65–70°F." Sow 3–4 seeds per hill, 1 inch deep. Thin to 2 plants per hill. Cucumbers grow fast in warm weather — vines can reach 6 feet and need a trellis or ample horizontal space.

Trellis-grown cucumbers produce straighter fruits and reduce fungal disease by keeping leaves off the ground. Per NC State Extension, "trellised cucumbers also yield more per square foot" than sprawling ground types.

Corn

Corn must be planted in blocks (minimum 4 rows wide) for adequate wind pollination. Per Penn State Extension, "planting corn in long, single rows produces poor pollination and incomplete ear fill." Sow in blocks, 12 inches apart, in rows 30–36 inches wide. Soil temperature must be at least 60°F; 65–70°F for sweet corn.

Basil

May is basil planting month in zones 5–7. Basil is a warm-season annual that thrives in heat but sulks and turns black in temperatures below 50°F. Per Clemson HGIC, "basil should be planted outdoors after the last frost when soil is at least 60°F."

I grow basil in every bed that has tomatoes in zone 7a — the traditional companion planting. Whether the companion effects are real is debated, but both plants thrive under the same conditions, and having basil close to tomatoes simplifies harvest.

Melons

Watermelons, cantaloupes, and honeydew melons need a long, hot growing season. Per Penn State Extension, "most melons need 75–100 days from transplant to harvest." In zone 5–6 with a May 15–30 last frost, melons are a stretch — grow from transplants (3-week-old starts) and choose short-season varieties.

In zone 7 with a mid-April last frost, direct sowing melons in late May is feasible for long-season varieties.

What to still start indoors in May

Zones 4–5: final indoor starts

Zone 5 gardeners (last frost May 25–30) can still start peppers, eggplant, and tomatoes in early May for a late-May/early-June outdoor planting. Per University of Minnesota Extension, "starting tomatoes in early May is appropriate for gardeners with a June 1 last frost date."

Succession lettuce and greens

May is not too late to start lettuce, chard, and kale indoors for transplanting in 4–6 weeks. A June planting of heat-tolerant lettuce varieties ('Jericho', 'Nevada') can produce through July in zones 5–6 with afternoon shade.

Cool-season crops in May: harvest and transition

In zone 7–8, May is the final harvest window for cool-season crops planted in early spring. Lettuce, spinach, and arugula will bolt as temperatures rise above 80°F.

Signs of bolting: Leaves become bitter, the plant center stretches upward, and a flower stalk begins to form. Once bolting starts, the leaves are unpleasant to eat. Per NC State Extension, "bolting is triggered by long day length and warm temperatures" — there is no stopping it once it starts.

Pull bolting plants and direct sow the beds with warm-season crops immediately after.

May ornamental planting

Annual flower bedding

May is the primary window for planting annual flowers in zones 5–7. Marigolds, zinnias, petunias, impatiens, vinca, and cosmos all go in after last frost.

Impatiens alternative: Due to impatiens downy mildew pressure, consider wax begonias or New Guinea impatiens for shaded beds. Per Penn State Extension, "beds with a history of impatiens downy mildew should not be replanted with common impatiens."

Dahlia tubers

Plant dahlia tubers after last frost in zone 5–7, when soil is above 60°F. Per Missouri Botanical Garden, plant "3–4 inches deep" with the eye facing up. Dahlias do not need to be soaked before planting.

Canna rhizomes

Plant canna rhizomes in May after last frost, when soil is above 60°F. I plant my stored cannas from the previous year in the first week of May in zone 7a.

Summer bulbs

Gladiolus, caladiums (zone 8+), and calla lily tubers all go in during May in zones 6–7. Per Missouri Botanical Garden, gladiolus should be planted in successive plantings (every 2 weeks through June) for a continuous bloom sequence rather than one mass bloom.

State planting calendars

• New York: /planting/ny/
• Pennsylvania: /planting/pa/
• New Jersey: /planting/nj/
• Illinois: /planting/il/
• Minnesota: /planting/mn/

Common mistakes

Frequently asked

How many tomato plants should I plant?

Per Penn State Extension, "one to two determinate plants or one indeterminate plant per person is typical for fresh-eating families." A single productive indeterminate tomato plant like 'Brandywine' or 'Cherokee Purple' can produce 15–25 pounds of fruit over the season. More plants means more canning or preserving capacity.

Can I direct sow tomatoes outdoors in May in zone 7?

You can, but the results will lag transplants by 3–6 weeks. Direct-sown tomatoes that germinate in late May will begin fruiting in September — at the tail end of the zone 7 growing season. If you choose this approach, use a determinate, short-season variety (60–70 days to maturity).

When can I plant sweet potatoes?

Per NC State Extension, sweet potatoes need warm soil — above 65°F — and a long growing season (90–120 days). In zone 7, plant sweet potato slips (rooted cuttings) in late May or early June. They need at least 4 months of warm growing time before fall frost.

Sources

1. Penn State Extension — Vegetable Planting
2. NC State Extension — Tomatoes and Vegetables
3. Clemson HGIC — Basil and Warm-Season Crops
4. University of Minnesota Extension — Vegetable Planting Calendar
5. Missouri Botanical Garden — Summer Bulbs