When to Plant Collard Greens in Duluth, MN
Published: April 24, 2026
Collard Green Planting Dates for Duluth, MN
| Start seeds indoors | April 2–9 |
| Last frost (average) | May 7 |
| Transplant outdoors | April 16–26 |
| Direct sow outdoors | April 16–26 |
| Minimum soil temperature | 45°F |
| Expect first harvest | June 15 – June 30 |
| Fall crop planting | July 23–August 2 |
| Fall crop harvest | September 21 |
| First fall frost (average) | October 1 |
⚠ 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 Duluth, MN
Consult a Duluth-area nursery or your state extension office for collard green varieties proven in Zone 4b.
Growing Collard Greens in Duluth
Duluth sits in Zone 4b, with an average last frost of May 7 and first fall frost around October 1 — giving a 147-day frost-free growing season. Cool-season crops like collard green benefit from Duluth's cooler spring and fall windows, when temperatures stay in the 55–75°F sweet spot that produces the best flavor and least bolting.
Duluth'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 Duluth is often more productive than the spring crop.
Duluth'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 Duluth
| Month | Task |
|---|---|
| April | Start seeds indoors under grow lights |
| May | Last frost — harden off seedlings outdoors |
| April | Transplant outdoors into warm soil |
| June | Expect first harvest window to open |
| July | Start fall crop — transplants or direct sow |
| October | First fall frost — harvest remaining, end of outdoor season |
Collard Green Tips for Duluth 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 Duluth 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 Duluth
- •Cabbage Worm — peaks July in Zone 4b (active June–August); green caterpillars on brassicas; apply Bt spray or use row covers.
- •Aphid — peaks July in Zone 4b (active June–August); monitor closely during peak season and treat early.
- •Flea Beetle — peaks July in Zone 4b (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 Duluth
In Duluth'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 Duluth, MN?
In Duluth (Zone 4b), start collard green seeds indoors around April 2–9 and transplant outdoors around April 16–26. The city's average last frost of May 7 is the anchor date — count 5 weeks back for seed starting and 3 weeks back for transplanting.
What zone is Duluth, MN for collard green growing?
Duluth is USDA Zone 4b. For collard green, this means a frost-free growing season of roughly 21 weeks running from May 7 to October 1. 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 Duluth?
Expect the first collard green harvest in Duluth around June 15, with harvest continuing through June 30. This is based on 60–75 days from transplant or direct sow. A fall crop planted July 23–August 2 adds a second harvest around September 21.
How long does it take to grow collard green in Duluth, MN?
From transplant or direct sow to first harvest, collard green takes 60–75 days in Duluth's climate. Based on a typical planting date of April 16–26, expect your first harvest around June 15. Duluth's cooler Zone 4b climate often lands at the slower end of this range — cooler nights slow fruit development.
What soil does collard green need in Duluth?
Duluth'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.