When to Plant Collard Greens in Wisconsin
Published: April 24, 2026
Wisconsin gardeners in Zone 5a have a 26-week frost-free window for collard green (April 15 to October 15). Cool-season crops like collard green do well here because the short, cool summers match the plant's temperature preferences naturally. This guide gives exact dates for Wisconsin based on your local frost calendar.
Collard Green Planting Dates for Wisconsin
| Start seeds indoors | March 11–18 |
| Last frost (average) | April 15 |
| Transplant outdoors | March 25–April 4 |
| Direct sow outdoors | March 25–April 4 |
| Expect first harvest | May 24 – June 8 |
| Fall crop start | August 6–16 |
| Fall harvest | October 5 |
| First fall frost (average) | October 15 |
Dates above assume Zone 5a, the most common zone in Wisconsin. Gardeners in cooler Milwaukee (Zone 5a) plant 1–2 weeks later; warmer Racine (Zone 5b) can plant 1–2 weeks earlier.
⚠ Direct sow or transplant collard greens 3–4 weeks before last frost. Extremely cold hardy — withstands temps to 15°F. Can be grown as a perennial in Zones 8+. Fall planting produces the best-flavored greens.
Growing Collard Greens in Wisconsin's Climate
Wisconsin's cold Zone 5a climate is close to ideal for collard green. The cool springs and moderate summers match the plant's natural temperature preferences, producing crisp, sweet, slow-bolting harvests that hot-climate gardeners cannot grow.
The fall collard green crop in Wisconsin is often better than the spring crop. Plants mature as temperatures cool in September and October, concentrating sugars and tightening heads or roots. Light frost can improve flavor; hard frost signals harvest time.
Common collard green pests to watch for in Wisconsin include Cabbage Worm and Aphid. The first line of defense is companion planting: Onion and Garlic planted nearby discourage several of these pests by confusing host-plant identification or repelling adults before they can lay eggs. Weekly garden walks in the early morning catch problems when they're still manageable.
Collard Green Garden Calendar for Wisconsin
| Month | Task | Notes |
|---|---|---|
| January | — | Dormant season |
| February | — | Dormant season |
| March | Transplant outdoors | Soil temp must be 45°F+; nighttime lows above 50°F |
| April | Harden off seedlings | Set seedlings outdoors 1–2 hours daily, increasing gradually |
| May ← | Watch for bolting | Harvest promptly; spring heat arrives quickly |
| June | — | Dormant season |
| July | — | Dormant season |
| August | Fall crop planting | Transplant or direct sow for fall harvest before frost |
| September | — | Dormant season |
| October | First frost approaches | Harvest remaining collard green; cover plants on frost nights |
| November | — | Dormant season |
| December | — | Dormant season |
Collard Green Growing Tips for Wisconsin Gardeners
- •Harvest outer leaves continuously once plants reach 10 inches — the central growing point produces for months.
- •In Zones 8+ collard greens often overwinter and produce for 2–3 years as a perennial.
- •Wisconsin's short growing season means start seeds indoors under grow lights — don't rely on windowsill light which produces leggy, weak seedlings that struggle outdoors.
- •Cover young transplants with floating row covers for the first 2–3 weeks outside. The 3–5°F of protection reduces frost damage risk and accelerates early growth.
- •Frost improves flavor dramatically — southern tradition is to wait for the first frost before harvesting.
Companion Planting for Collard Greens in Wisconsin
In Wisconsin's cold climate, planting collard green with Onion and Garlic helps deter pests and improve soil. Avoid planting near Tomato and Strawberry, which inhibit collard green growth through root chemistry or shared pest pressure. See the full collard green companion planting guide for the complete list.
Collard Greens Planting Dates by City in Wisconsin
Top cities in Wisconsin — select for city-level frost dates and planting calendars.
Frequently Asked Questions
When should I plant collard green in Wisconsin?
In Wisconsin (Zone 5a), start collard green seeds indoors around March 11–18 and transplant outdoors around March 25–April 4 — 3 weeks before the state's average last frost of April 15.
What is the last frost date in Wisconsin?
Wisconsin's average last frost date is April 15 in the state's most common Zone 5a. Frost dates vary by city — higher elevations and northern counties run 1 to 3 weeks later than the state average. See the city list below for city-level frost dates.
Can I grow collard green year-round in Wisconsin?
collard green is a cool-season crop in Wisconsin, with spring and fall windows. Summer heat bolts the plants before they can produce a harvestable crop. Succession planting every 2–3 weeks stretches the harvest window.
What collard green varieties grow best in Wisconsin?
For Wisconsin's Zone 5a, consult a local nursery or extension office for collard-greens variety recommendations.
When do I start collard green seeds indoors in Wisconsin?
Start collard green seeds indoors in Wisconsin around March 11–18, which is 5 weeks before the state's average last frost of April 15. Use grow lights and keep soil temperatures at 70–75°F for fastest germination.