When to plant brussels sprouts in Oklahoma City, Oklahoma

March 7 – March 21

Transplant outdoors · typical Oklahoma City year

Climate basis: NOAA station Oklahoma City Will Rogers AP, OK (USW00013967), 7 mi (12 km) from downtown Oklahoma City (ZCTA 73102 centroid), elevation 1285 ft, on the 1991–2020 climate normals. Transplant brussels sprouts outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (April 4). One year in ten still freezes after April 20.

Last spring freezeApril 41-in-10 after Apr 20

First fall freezeNovember 21-in-10 before Oct 21

Frost-free season≈ 213 daysmedian at 32°F

Hard freeze, 28°Mar 21 – Nov 11kills even hardy greens

USDA zone7b5 to 10°F winter low — not frost timing

The Oklahoma City year

Start seeds indoorsJan 24 – Feb 7

Transplant outdoorsMar 7 – Mar 21

indoors under lights
in the garden
frost-free season
1-in-10 years still freeze to Apr 20

Brussels sprouts in Oklahoma City · freeze context from Oklahoma City Will Rogers AP, OK, 1991–2020 normals.

Every method, with its sources

Start seeds indoors

Jan 24 – Feb 7

Sow 4–6 weeks before the set-out window opens (UNH 4–6 weeks; Missouri G6570 6–8 weeks). Anchored to the median last spring freeze (Apr 4). University of New Hampshire Extension · University of Missouri Extension

Transplant outdoors

Mar 7 – Mar 21

UNH: set out 2–4 weeks before the last frost; Purdue's hardy class allows 4–6 weeks before. The later UNH range is used. Anchored to the median last spring freeze (Apr 4). University of New Hampshire Extension · Purdue University Extension

Variety assumption: A long-season crop (about 90–110 days from transplant); sprouts sweeten after light fall frosts.

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 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.
University of Missouri Extension: Starting Plants Indoors from Seeds (G6570) (accessed 2026-07-24)
Weeks needed to grow vegetable transplants indoors (Table 2).
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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