PlantingWindowThe American Planting Almanac

When to plant collards in Tulsa, Oklahoma

March 17 – March 31

Direct-sow outdoors · typical Tulsa year

Climate basis: NOAA station Tulsa INTL AP, OK (USW00013968), 7 mi (11 km) from downtown Tulsa (ZCTA 74103 centroid), elevation 650 ft, on the 1991–2020 climate normals. Direct-sow collards from approximately the dates above, anchored to the median last spring 32°F freeze (March 31). One year in ten still freezes after April 15.

Last spring freezeMarch 311-in-10 after Apr 15
First fall freezeNovember 41-in-10 before Oct 20
Frost-free season≈ 220 daysmedian at 32°F
Hard freeze, 28°Mar 17 – Nov 13kills even hardy greens
USDA zone7b5 to 10°F winter low — not frost timing

The Tulsa year

Direct-sow outdoorsMar 17 – Mar 31
Fall plantingSep 9 – Oct 7
  • indoors under lights
  • in the garden
  • frost-free season
  • 1-in-10 years still freeze to Apr 15
Collards in Tulsa · freeze context from Tulsa INTL AP, OK, 1991–2020 normals.

Every method, with its sources

Direct-sow outdoors

Mar 17 – Mar 31

Purdue: hardy — 4–6 weeks before the last frost; Penn State's earliest sowing Apr 17 (−14 days) is the later start and is used. Anchored to the median last spring freeze (Mar 31). Penn State Extension (York County Master Gardeners) · Purdue University Extension

Fall planting

Sep 9 – Oct 7

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

Variety assumption: Assumes an average variety (about 70–80 days; Penn State lists 80).

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)

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