Michigan planting calendar

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

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

Leeks planting timetable for Michigan

Stage	When in Michigan	Anchor
Start seeds indoors	early March (March 6)	10 weeks before the last frost (mid-May)
Transplant outside	mid-April (April 17)	28 days before the last frost (mid-May)
First harvest (estimate)	mid-August (August 15)	~120 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 leeks 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. Sow early — leeks bolt once daytime temperatures hold above 24 °C, so the earlier they go in, the longer the harvest.

Leeks are among the hardiest alliums — established plants tolerate temperatures as low as -10 °C, making them a reliable overwintering crop in zones 5–9. Start seeds indoors 10–12 weeks before last frost, transplanting pencil-thick seedlings into 15 cm (6-inch) deep holes or trenches to blanch the stems; backfill gradually as plants grow. Early-season varieties mature in around 90 days; late-season types take up to 150 days and deliver the best cold-hardiness for autumn and winter harvest.

Frost-risk note

Don't plant before mid-May — a hard freeze can still set young plants back. 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

The same early window suits peas, lettuce, spinach, and onion sets.

Quick-grow guide

Sun: Full sun — 6+ hours direct.
Soil temperature for germination: 7-25 °C (45-77 °F).
Spacing: 6 inches (15 cm) between plants.
Days to harvest: ~120 days from planting out.

Frequently asked questions

When is the best time to plant leeks in Michigan?

In Michigan (mostly USDA zone 6a), sow leeks indoors around early March, transplant outdoors mid-April (before the last frost, mid-May), and harvest from mid-August. Leeks are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

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 leeks in Michigan?

Yes. Michigan's dominant zone 6a supports leeks — the key is timing. Leeks are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

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?

The same early window suits peas, lettuce, spinach, and onion sets.

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.