When to plant chinese cabbage (napa) in Denver, Colorado

April 9 – April 16

Transplant outdoors · typical Denver year

Climate basis: NOAA station Denver Water Dept, CO (USC00052223), 2 mi (3 km) from downtown Denver (ZCTA 80202 centroid), elevation 5228 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 (April 30). One year in ten still freezes after May 13.

Last spring freezeApril 301-in-10 after May 13

First fall freezeOctober 121-in-10 before Sep 28

Frost-free season≈ 165 daysmedian at 32°F

Hard freeze, 28°Apr 18 – Oct 21kills even hardy greens

USDA zone6a-10 to -5°F winter low — not frost timing

The Denver year

Start seeds indoorsMar 5 – Mar 19

Transplant outdoorsApr 9 – Apr 16

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 13

Chinese Cabbage (Napa) in Denver · freeze context from Denver Water Dept, CO, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Mar 5 – Mar 19

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 (Apr 30). 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 9 – Apr 16

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 (Apr 30). 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)

Keep exploring

This crop, other cities

Related crops in Denver

Local overview