When to plant chinese cabbage (napa) in Billings, Montana

April 19 – April 26

Transplant 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. Transplant chinese cabbage (napa) outdoors 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

Start seeds indoorsMar 15 – Mar 29

Transplant outdoorsApr 19 – Apr 26

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 24

Chinese Cabbage (Napa) in Billings · freeze context from Billings Wtp, MT, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Mar 15 – Mar 29

Arkansas Extension requires transplants no older than "four to five weeks" at setting out, so indoor sowing is counted back 28–35 days from the cited transplant window, giving last spring frost minus 56 to minus 42 days. Anchored to the median last spring freeze (May 10). University of Arkansas System Division of Agriculture, Cooperative Extension Service · Clemson Cooperative Extension, Home & Garden Information Center · Clemson Cooperative Extension, Home & Garden Information Center

Transplant outdoors

Apr 19 – Apr 26

Arkansas Extension states "Transplant two to three weeks before the last frost-free date", giving last spring frost minus 21 to minus 14 days; Clemson's warning that spring-frosted seedlings bolt is a caution on the same window, not a competing interval. Anchored to the median last spring freeze (May 10). Clemson Cooperative Extension, Home & Garden Information Center · Clemson Cooperative Extension, Home & Garden Information Center

Variety assumption: Offsets assume spring-set transplants of the 45–72 day Napa and Michihili types tabulated by Arkansas Extension; no fall window is encoded because every fall rule found for napa is fixed-calendar ("early to midsummer", "July") rather than frost-anchored.

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 (3)

University of Arkansas System Division of Agriculture, Cooperative Extension Service: Chinese Cabbage (Home Gardening Series, FSA6066) (accessed 2026-07-25)
"Transplant two to three weeks before the last frost-free date and before the plants are too old (four to five weeks)."
Clemson Cooperative Extension, Home & Garden Information Center: Chinese Vegetables (accessed 2026-07-25)
"Chinese cabbage is best sown in late summer and autumn rather than spring. If seed is sown in spring, young plants may bolt if they are frosted or exposed to long, cold nights."
Clemson Cooperative Extension, Home & Garden Information Center: Cabbage & Chinese Cabbage (accessed 2026-07-25)

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