PlantingWindowThe American Planting Almanac

When to plant turnips in Boise, Idaho

April 19 – May 3

Direct-sow outdoors · typical Boise year

Climate basis: NOAA station Boise 7 N, ID (USC00101017), 6 mi (9 km) from downtown Boise (ZCTA 83702 centroid), elevation 3885 ft, on the 1991–2020 climate normals. Direct-sow turnips from approximately the dates above, anchored to the median last spring 32°F freeze (May 17). One year in ten still freezes after June 10.

Last spring freezeMay 171-in-10 after Jun 10
First fall freezeOctober 121-in-10 before Sep 27
Frost-free season≈ 147 daysmedian at 32°F
Hard freeze, 28°Apr 27 – Oct 24kills even hardy greens
USDA zone7a0 to 5°F winter low — not frost timing

The Boise year

Direct-sow outdoorsApr 19 – May 3
Fall plantingAug 17 – Sep 14
  • indoors under lights
  • in the garden
  • frost-free season
  • 1-in-10 years still freeze to Jun 10
Turnips in Boise · freeze context from Boise 7 N, ID, 1991–2020 normals.

Every method, with its sources

Direct-sow outdoors

Apr 19 – May 3

Purdue: hardy — 4–6 weeks before the last frost; Penn State's earliest sowing Apr 3 (−28 days) is the later start and is used. Anchored to the median last spring freeze (May 17). Penn State Extension (York County Master Gardeners) · Purdue University Extension

Fall planting

Aug 17 – Sep 14

Purdue Table 2: plant fall turnips 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 variety (about 45–60 days; Penn State lists 55).

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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