When to plant zucchini / summer squash in Michigan
Michigan’s average last spring frost is May 10, and the first fall frost typically arrives around October 5 — about 148 frost-free days (USDA zones 4a, 4b, 5a, 5b, 6a, 6b). Zucchini / Summer Squash needs 45–60 days to mature, which fits comfortably within Michigan's growing season.
Michigan covers a wide range of climates, so your exact frost dates may differ from the state average by two weeks or more. For dates tuned to your town, use the calendar generator.
When to plant zucchini / summer squash in Michigan: the short answer
For a spring planting, plant out May 10 – May 27, with seeds started indoors Apr 12 – Apr 26. Wait until the soil is at least 60°F and frost is over.
Succession sow again in Michigan: Jun 14 · Jul 12
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow zucchini / summer squash in Michigan, step by step
- Start seeds indoors (Apr 12 – Apr 26). Sow seeds 1 inch deep in seed-starting mix under bright light. They take 5-10 days to sprout, fastest in soil around 85°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. It needs at least six to eight hours of direct sun a day and loose soil at least 14 inches deep, with a pH between 5.5 and 7.5. Dig in compost before planting.
- Plant out (May 10 – May 27). Space plants about 30 inches apart in rows 42 inches apart. It is killed by frost, so nothing goes outside until the danger has passed.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: squash vine borer, squash bug, striped cucumber beetle, aphids. Diseases and disorders: powdery mildew, bacterial wilt, blossom-end rot (calcium disorder).
- Harvest (from about Jul 1 – Jul 16). Zucchini / Summer Squash takes 45-60 days to reach harvest. One or two plants feed a household. A second sowing in early-mid summer dodges the first vine borer generation.
Figures come from our crop data; dates use Michigan’s average frost dates. More in the full zucchini / summer squash growing guide.
Zucchini planting dates by USDA zone in Michigan
Michigan spans USDA zones 4a, 4b, 5a, 5b, 6a, 6b. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the zucchini / summer squash dates shift with them.
When to plant zucchini / summer squash in nearby states
Questions gardeners in Michigan ask
When is the best time to plant zucchini / summer squash in Michigan?
Plant zucchini / summer squash transplants outdoors in Michigan between May 10 and May 27. That timing is set by Michigan's average last spring frost of May 10; Michigan spans several climates, so cooler and higher parts of the state run later.
When should I start zucchini / summer squash seeds indoors in Michigan?
Start seeds indoors between April 12 and April 26, about 3 weeks before the last frost, so the seedlings are ready to plant out from May 10.
Can I plant zucchini / summer squash in the fall in Michigan?
Yes. For a fall crop, sow between July 3 and July 20, so the crop matures in cool weather before Michigan's first frost around October 5.
When will zucchini / summer squash planted in Michigan be ready to harvest?
Planted on time, zucchini / summer squash is usually ready from about July 1 to July 16, 45-60 days after planting.
When is the last frost in Michigan?
On average around May 10, with the first fall frost around October 5 - about 148 frost-free days. Your town may differ by two weeks or more.