When to plant brussels sprouts in St. Louis, Missouri
March 4 – March 18
Transplant outdoors · typical St. Louis yearClimate basis: NOAA station St Louis Sci Ctr, MO (USC00237452), 4 mi (7 km) from downtown St. Louis (ZCTA 63101 centroid), elevation 515 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 1). One year in ten still freezes after April 18.
The St. Louis year
- indoors under lights
- in the garden
- frost-free season
- 1-in-10 years still freeze to Apr 18
Every method, with its sources
Start seeds indoors
Jan 21 – Feb 4Sow 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 1). University of New Hampshire Extension · University of Missouri Extension
Transplant outdoors
Mar 4 – Mar 18UNH: 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 1). 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.
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.