PlantingWindowThe American Planting Almanac

When to plant collards in Knoxville, Tennessee

March 28 – April 11

Direct-sow outdoors · typical Knoxville year

Climate basis: NOAA station Knoxville Exp Stn, TN (USC00404946), 5 mi (8 km) from downtown Knoxville (ZCTA 37902 centroid), elevation 830 ft, on the 1991–2020 climate normals. Direct-sow collards from approximately the dates above, anchored to the median last spring 32°F freeze (April 11). One year in ten still freezes after April 29.

Last spring freezeApril 111-in-10 after Apr 29
First fall freezeOctober 281-in-10 before Oct 13
Frost-free season≈ 198 daysmedian at 32°F
Hard freeze, 28°Mar 31 – Nov 6kills even hardy greens
USDA zone7b5 to 10°F winter low — not frost timing

The Knoxville year

Direct-sow outdoorsMar 28 – Apr 11
Fall plantingSep 2 – Sep 30
  • indoors under lights
  • in the garden
  • frost-free season
  • 1-in-10 years still freeze to Apr 29
Collards in Knoxville · freeze context from Knoxville Exp Stn, TN, 1991–2020 normals.

Every method, with its sources

Direct-sow outdoors

Mar 28 – Apr 11

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 (Apr 11). Penn State Extension (York County Master Gardeners) · Purdue University Extension

Fall planting

Sep 2 – Sep 30

Purdue Table 2: plant fall collards at least 4–8 weeks before the first fall frost. Anchored to the median first fall freeze (Oct 28). 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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