Michigan planting calendar

When to plant winter squash in Michigan — sow, transplant & harvest dates

Michigan is mostly USDA zone 6a (range 4a-6b). Dates below are derived from winter squash's frost tolerance and Michigan's frost window — not generic national averages.

Winter squash planting timetable for Michigan

Stage	When in Michigan	Anchor
Start seeds indoors	late April (April 24)	3 weeks before the last frost (mid-May)
Transplant outside	late May (May 29)	14 days after the last frost (mid-May)
First harvest (estimate)	early September (September 1)	~95 days from transplant

Dates are state-wide averages for the dominant zone. Local microclimates — elevation, urban heat, coastal moderation — can shift the window by 1-2 weeks. Use the frost-date calculator for a date tuned to your town.

Why Michigan's climate shifts the winter squash dates

Michigan's last spring frost averages mid-May and first fall frost early October, which sets the whole planting clock. Michigan is moderated by the Great Lakes, which create a milder fruit belt along Lake Michigan and a colder interior Upper Peninsula. Wait for warm soil — winter squash stall in cold ground even after the air warms, so don't rush them out.

Winter squash (butternut, acorn, delicata, Hubbard) requires 85-110 frost-free days from transplant; plan backward from the first fall frost date before seeding. Minimum soil temperature is 18 °C (65 °F); seeds rot in cold, wet soil. Short-season gardeners in zones 3-4 benefit from a 2-3 week indoor start in biodegradable pots to avoid transplant shock to the taproot. Curing harvested fruit at 27-30 °C for 10-14 days extends storage life.

Frost-risk note

Don't plant before mid-May — even a light frost will kill seedlings overnight. In the western Upper Peninsula interior (zone 4a) the safe date runs a week or two later.

Regional variation within Michigan

the western Upper Peninsula interior (zone 4a) runs roughly 1-2 weeks behind the state average; the southeast near Detroit and the Lake Michigan fruit belt (zone 6b) can plant 1-2 weeks earlier.

Detroit — USDA zone 6b
Grand Rapids — USDA zone 6a
Lansing — USDA zone 5b
Marquette — USDA zone 5a
Traverse City — USDA zone 6a

What else to plant in Michigan around then

Pair the post-frost slot with other warm-season crops — peppers, beans, squash, and cucumbers.

Quick-grow guide

Sun: Full sun — 6-8 hours direct.
Soil temperature for germination: 21-29 °C (70-85 °F).
Spacing: 48-72 inches (120-180 cm) for vining types; 24-36 inches (60-90 cm) for compact types between plants.
Days to harvest: ~95 days from planting out.

Frequently asked questions

When is the best time to plant winter squash in Michigan?

In Michigan (mostly USDA zone 6a), sow winter squash indoors around late April, transplant outdoors late May (after the last frost, mid-May), and harvest from early September. Winter squash are frost-tender — a single light frost kills seedlings, so they only go outside once frost danger has fully passed and the soil is warm.

What USDA zone is Michigan?

Most of Michigan sits in USDA hardiness zone 6a, with the state spanning roughly 4a-6b from the western Upper Peninsula interior (zone 4a) to the southeast near Detroit and the Lake Michigan fruit belt (zone 6b). The last spring frost averages mid-May and the first fall frost early October.

Can you grow winter squash in Michigan?

Yes. Michigan's dominant zone 6a supports winter squash — the key is timing. Winter squash are frost-tender — a single light frost kills seedlings, so they only go outside once frost danger has fully passed and the soil is warm.

Does the planting date change across Michigan?

the western Upper Peninsula interior (zone 4a) runs roughly 1-2 weeks behind the state average; the southeast near Detroit and the Lake Michigan fruit belt (zone 6b) can plant 1-2 weeks earlier.

What else can I plant in Michigan around the same time?

Pair the post-frost slot with other warm-season crops — peppers, beans, squash, and cucumbers.

Source and methodology

State zone spans from the USDA Plant Hardiness Zone Map (2023); frost-date averages from NOAA Climate Data Online. Hot-state two-season timing cross-checked against the UF/IFAS Florida Gardening Calendar and the University of Arizona Cooperative Extension planting calendar. Curated by the Growli editorial team.