PlantingWindowThe American Planting Almanac

When to plant kale in Denver, Colorado

April 9 – April 23

Direct-sow outdoors · typical Denver year

Climate basis: NOAA station Denver Water Dept, CO (USC00052223), 2 mi (3 km) from downtown Denver (ZCTA 80202 centroid), elevation 5228 ft, on the 1991–2020 climate normals. Direct-sow kale from approximately the dates above, anchored to the median last spring 32°F freeze (April 30). One year in ten still freezes after May 13.

Last spring freezeApril 301-in-10 after May 13
First fall freezeOctober 121-in-10 before Sep 28
Frost-free season≈ 165 daysmedian at 32°F
Hard freeze, 28°Apr 18 – Oct 21kills even hardy greens
USDA zone6a-10 to -5°F winter low — not frost timing

The Denver year

Direct-sow outdoorsApr 9 – Apr 23
Fall plantingAug 17 – Sep 14
  • indoors under lights
  • in the garden
  • frost-free season
  • 1-in-10 years still freeze to May 13
Kale in Denver · freeze context from Denver Water Dept, CO, 1991–2020 normals.

Every method, with its sources

Direct-sow outdoors

Apr 9 – Apr 23

Purdue: hardy — 4–6 weeks before the last frost; Penn State's earliest sowing Apr 10 (−21 days) is the later start and is used. Anchored to the median last spring freeze (Apr 30). Penn State Extension (York County Master Gardeners) · Purdue University Extension

Fall planting

Aug 17 – Sep 14

Purdue Table 2: plant fall kale at least 4–8 weeks before the first fall frost. Anchored to the median first fall freeze (Oct 12). Purdue University Extension

Variety assumption: Assumes an average curly variety (about 50–65 days; Penn State lists 60).

These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.

This week, not a typical year:
Crop rule sources (2)

Keep exploring

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