When to plant kohlrabi in Milwaukee, Wisconsin

March 29 – April 12

Transplant outdoors · typical Milwaukee year

Climate basis: NOAA station West Allis, WI (USC00479046), 6 mi (10 km) from downtown Milwaukee (ZCTA 53202 centroid), elevation 723 ft, on the 1991–2020 climate normals. Transplant kohlrabi outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (April 26). One year in ten still freezes after May 12.

Last spring freezeApril 261-in-10 after May 12

First fall freezeOctober 221-in-10 before Oct 7

Frost-free season≈ 177 daysmedian at 32°F

Hard freeze, 28°Apr 14 – Nov 1kills even hardy greens

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

The Milwaukee year

Start seeds indoorsFeb 15 – Mar 1

Transplant outdoorsMar 29 – Apr 12

Fall plantingAug 27 – Sep 24

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to May 12

Kohlrabi in Milwaukee · freeze context from West Allis, WI, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Feb 15 – Mar 1

Sow 4–6 weeks before the set-out window opens (UNH: time from seed to transplant 4–6 weeks). Anchored to the median last spring freeze (Apr 26). University of New Hampshire Extension

Transplant outdoors

Mar 29 – Apr 12

UNH: safe to set out 4 weeks before the last frost; Purdue's hardy class allows 4–6 weeks before. The later UNH start is used. Anchored to the median last spring freeze (Apr 26). University of New Hampshire Extension · Purdue University Extension

Fall planting

Aug 27 – Sep 24

Purdue Table 2: plant fall kohlrabi at least 4–8 weeks before the first fall frost. Anchored to the median first fall freeze (Oct 22). 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 (2)

University of New Hampshire Extension: Growing Vegetables: When to Plant Your Vegetable Garden [fact sheet] (accessed 2026-07-24)
Per-crop 'time from seed to transplant' and 'safe to set out in garden' relative to last frost.
Purdue University Extension: Indiana Vegetable Planting Calendar (HO-186-W) (accessed 2026-07-24)
Hardiness classes: hardy = plant 4-6 wk before last spring frost; semi-hardy = 2-4 wk before; tender = after average last frost; very tender = at least 2 wk after. Table 2: fall planting at least 4-8 wk before first fall frost.

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