When to plant broccoli in Chicago, Illinois
March 13 – March 27
Transplant outdoors · typical Chicago yearClimate basis: NOAA station Chicago Northerly Is, IL (USC00111550), 2 mi (3 km) from downtown Chicago (ZCTA 60602 centroid), elevation 583 ft, on the 1991–2020 climate normals. Transplant broccoli outdoors from approximately the dates above, anchored to the median last spring 32°F freeze (April 10). One year in ten still freezes after April 25.
The Chicago year
- indoors under lights
- in the garden
- frost-free season
- 1-in-10 years still freeze to Apr 25
Every method, with its sources
Start seeds indoors
Jan 30 – Feb 13Sow 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 10). University of New Hampshire Extension · University of Missouri Extension
Transplant outdoors
Mar 13 – Mar 27UNH: 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 10). University of New Hampshire Extension · Purdue University Extension
Fall planting
Sep 10 – Oct 8Purdue Table 2: plant fall broccoli at least 4–8 weeks before the first fall frost. Anchored to the median first fall freeze (Nov 5). Purdue University Extension
Variety assumption: Assumes an average heading variety (about 60–70 days from transplant).
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.