Wisconsin planting calendar

When to plant collard greens in Wisconsin — sow, transplant & harvest dates

Wisconsin is mostly USDA zone 5a (range 3b-6a). Dates below are derived from collard greens's frost tolerance and Wisconsin's frost window — not generic national averages.

Collard Greens planting timetable for Wisconsin

Stage	When in Wisconsin	Anchor
Start seeds indoors	mid-April (April 17)	4 weeks before the last frost (mid-May)
Transplant outside	late April (April 24)	21 days before the last frost (mid-May)
First harvest (estimate)	early July (July 3)	~70 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 Wisconsin's climate shifts the collard greens dates

Wisconsin's last spring frost averages mid-May and first fall frost early October, which sets the whole planting clock. Wisconsin is a cold, continental Midwest state, milder along Lake Michigan and considerably colder in the northern interior. Sow early — collard greens bolt once daytime temperatures hold above 24 °C, so the earlier they go in, the longer the harvest.

Collards are one of the hardiest brassicas, tolerating temperatures down to about -7 °C once established, and one of the most heat-tolerant — unlike kale or cabbage, they continue producing in summer heat above 32 °C, which is why they are a staple in Zones 7–9 year-round. Transplant 2–4 weeks before last spring frost, or direct-sow where the season allows; for a fall harvest, start transplants 8–10 weeks before first fall frost. Succession-plant for continuous leaf harvest.

Frost-risk note

Don't plant before mid-May — a hard freeze can still set young plants back. In the north-central highlands near the UP line (zone 3b) the safe date runs a week or two later.

Regional variation within Wisconsin

the north-central highlands near the UP line (zone 3b) runs roughly 1-2 weeks behind the state average; the Lake Michigan shore around Milwaukee (zone 6a) can plant 1-2 weeks earlier.

Milwaukee — USDA zone 6a
Madison — USDA zone 5b
Green Bay — USDA zone 5a
Eau Claire — USDA zone 4b

What else to plant in Wisconsin 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: 7-29 °C (45-85 °F).
Spacing: 18-24 inches (45-60 cm) between plants.
Days to harvest: ~70 days from planting out.

Frequently asked questions

When is the best time to plant collard greens in Wisconsin?

In Wisconsin (mostly USDA zone 5a), sow collard greens indoors around mid-April, transplant outdoors late April (before the last frost, mid-May), and harvest from early July. Collard Greens 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 Wisconsin?

Most of Wisconsin sits in USDA hardiness zone 5a, with the state spanning roughly 3b-6a from the north-central highlands near the UP line (zone 3b) to the Lake Michigan shore around Milwaukee (zone 6a). The last spring frost averages mid-May and the first fall frost early October.

Can you grow collard greens in Wisconsin?

Yes. Wisconsin's dominant zone 5a supports collard greens — the key is timing. Collard Greens 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 Wisconsin?

the north-central highlands near the UP line (zone 3b) runs roughly 1-2 weeks behind the state average; the Lake Michigan shore around Milwaukee (zone 6a) can plant 1-2 weeks earlier.

What else can I plant in Wisconsin 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.