PlantingWindowThe American Planting Almanac

When to plant mustard greens in Billings, Montana

April 12 – April 26

Direct-sow outdoors · typical Billings year

Climate basis: NOAA station Billings Wtp, MT (USC00240802), 13 mi (21 km) from downtown Billings (ZCTA 59101 centroid), elevation 3097 ft, on the 1991–2020 climate normals. Direct-sow mustard greens from approximately the dates above, anchored to the median last spring 32°F freeze (May 10). One year in ten still freezes after May 24.

Last spring freezeMay 101-in-10 after May 24
First fall freezeOctober 11-in-10 before Sep 19
Frost-free season≈ 142 daysmedian at 32°F
Hard freeze, 28°Apr 27 – Oct 12kills even hardy greens
USDA zone5a-20 to -15°F winter low — not frost timing

The Billings year

Direct-sow outdoorsApr 12 – Apr 26
Fall plantingAug 6 – Sep 3
  • indoors under lights
  • in the garden
  • frost-free season
  • 1-in-10 years still freeze to May 24
Mustard greens in Billings · freeze context from Billings Wtp, MT, 1991–2020 normals.

Every method, with its sources

Direct-sow outdoors

Apr 12 – Apr 26

Purdue lists mustard under both hardy (4–6 weeks before the last frost) and semi-hardy (2–4 weeks before); the later semi-hardy start is used. Anchored to the median last spring freeze (May 10). Purdue University Extension

Fall planting

Aug 6 – Sep 3

Purdue Table 2: plant fall mustard greens at least 4–8 weeks before the first fall frost. Anchored to the median first fall freeze (Oct 1). Purdue University Extension

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 (1)

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