When to Plant Collard Greens in Green Bay, WI
Published: April 24, 2026
Collard Green Planting Dates for Green Bay, WI
| Start seeds indoors | March 11–18 |
| Last frost (average) | April 15 |
| Transplant outdoors | March 25–April 4 |
| Direct sow outdoors | March 25–April 4 |
| Minimum soil temperature | 45°F |
| Expect first harvest | May 24 – June 8 |
| Fall crop planting | August 6–16 |
| Fall crop harvest | October 5 |
| First fall frost (average) | October 15 |
⚠ 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.
Best Collard Green Varieties for Green Bay, WI
Consult a Green Bay-area nursery or your state extension office for collard green varieties proven in Zone 5a.
Growing Collard Greens in Green Bay
Green Bay sits in Zone 5a, with an average last frost of April 15 and first fall frost around October 15 — giving a 183-day frost-free growing season. Cool-season crops like collard green benefit from Green Bay's cooler spring and fall windows, when temperatures stay in the 55–75°F sweet spot that produces the best flavor and least bolting.
Green Bay's cooler summers are close to ideal for collard green. The same conditions that limit tomato and pepper yields benefit cool-season crops — slower bolting, sweeter flavor, and longer harvest windows. The fall collard green crop in Green Bay is often more productive than the spring crop.
Green Bay's clay-loam soils are productive but benefit from annual compost amendment — 2 to 3 inches worked in before planting improves drainage and nutrient availability for collard green. Consistent watering (1 inches per week) paired with organic mulch maintains the even moisture that clay-loam holds well. Avoid working wet soil in spring, which causes severe compaction in clay-loam blends.
Collard Green Calendar for Green Bay
| Month | Task |
|---|---|
| March | Start seeds indoors under grow lights |
| April | Last frost — harden off seedlings outdoors |
| March | Transplant outdoors into warm soil |
| May | Expect first harvest window to open |
| August | Start fall crop — transplants or direct sow |
| October | First fall frost — harvest remaining, end of outdoor season |
Collard Green Tips for Green Bay 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.
- •Fall plantings in Green Bay often out-produce spring plantings — cooler temperatures slow bolting and concentrate flavor. Light frost can actually improve the taste of collard green.
Common Collard Green Pests in Green Bay
- •Cabbage Worm — peaks July in Zone 5a (active June–August); green caterpillars on brassicas; apply Bt spray or use row covers.
- •Aphid — peaks July in Zone 5a (active June–August); monitor closely during peak season and treat early.
- •Flea Beetle — peaks July in Zone 5a (active June–August); tiny black beetles that riddle leaves with holes; row covers protect seedlings.
Check plants every 2–3 days during peak season — early intervention prevents most infestations from becoming serious.
What to Plant with Collard Greens in Green Bay
In Green Bay's cold climate, Onion and Garlic are the most beneficial plants to grow alongside collard green. Onion deters carrot fly, aphids, and several root-zone pests through sulfur compounds. Keep collard green away from Tomato — it competes for nutrients or shares pest pressure. In short-season gardens, interplanting companions at transplant time maximizes each bed's productive weeks.
Frequently Asked Questions
When should I plant collard green in Green Bay, WI?
In Green Bay (Zone 5a), start collard green seeds indoors around March 11–18 and transplant outdoors around March 25–April 4. The city's average last frost of April 15 is the anchor date — count 5 weeks back for seed starting and 3 weeks back for transplanting.
What zone is Green Bay, WI for collard green growing?
Green Bay is USDA Zone 5a. For collard green, this means a frost-free growing season of roughly 26 weeks running from April 15 to October 15. Cool-season crops like collard green thrive in this zone with both spring and fall planting windows available.
When is collard green harvest season in Green Bay?
Expect the first collard green harvest in Green Bay around May 24, with harvest continuing through June 8. This is based on 60–75 days from transplant or direct sow. A fall crop planted August 6–16 adds a second harvest around October 5.
How long does it take to grow collard green in Green Bay, WI?
From transplant or direct sow to first harvest, collard green takes 60–75 days in Green Bay's climate. Based on a typical planting date of March 25–April 4, expect your first harvest around May 24. Green Bay's cooler Zone 5a climate often lands at the slower end of this range — cooler nights slow fruit development.
What soil does collard green need in Green Bay?
Green Bay's clay-loam soil is productive for collard green but benefits from annual compost amendment. Work 2–3 inches of compost into the top 10 inches before planting. Avoid working wet soil in spring — clay-loam compacts badly when wet. Consistent watering paired with organic mulch maintains the even moisture these soils hold well.