When to plant broccoli in Wisconsin
Wisconsin’s average last spring frost is May 10, and the first fall frost typically arrives around September 30 — about 143 frost-free days (USDA zones 3b, 4a, 4b, 5a, 5b). Broccoli needs 60–85 days to mature, which fits comfortably within Wisconsin's growing season.
When to plant broccoli in Wisconsin: the short answer
For a spring planting, plant out Apr 19 – May 6, with seeds started indoors Mar 22 – Apr 5. Seeds germinate in soil from 45 to 85°F.
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow broccoli in Wisconsin, step by step
- Start seeds indoors (Mar 22 – Apr 5). Sow seeds ½ inch deep in seed-starting mix under bright light. They take 5-10 days to sprout, fastest in soil around 75°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. It needs at least six to eight hours of direct sun a day and loose soil at least 18 inches deep, with a pH between 6.0 and 7.0. Dig in compost before planting.
- Plant out (Apr 19 – May 6). Space plants about 18 inches apart in rows 30 inches apart. It tolerates a light frost but not a hard freeze. As a cool-season crop it does best before summer heat arrives in Wisconsin.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: cabbage worm, cabbage looper, aphids, flea beetle, cabbage root maggot. Diseases and disorders: clubroot, black rot, downy mildew.
- Harvest (from about Jun 25 – Jul 20). Broccoli takes 60-85 days to reach harvest. Days to maturity counted from transplant. Keep cutting side shoots after the main head for weeks. Spring crop must size up before heat or it buttons.
Figures come from our crop data; dates use Wisconsin’s average frost dates. More in the full broccoli growing guide.
Broccoli planting dates by USDA zone in Wisconsin
Wisconsin spans USDA zones 3b, 4a, 4b, 5a, 5b. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the broccoli dates shift with them.
When to plant broccoli in nearby states
Questions gardeners in Wisconsin ask
When is the best time to plant broccoli in Wisconsin?
Plant broccoli transplants outdoors in Wisconsin between April 19 and May 6. That timing is set by Wisconsin's average last spring frost of May 10.
When should I start broccoli seeds indoors in Wisconsin?
Start seeds indoors between March 22 and April 5, about 6 weeks before the last frost, so the seedlings are ready to plant out from April 19.
Can I plant broccoli in the fall in Wisconsin?
Yes. For a fall crop, start transplants between June 21 and July 8, so the crop matures in cool weather before Wisconsin's first frost around September 30.
When will broccoli planted in Wisconsin be ready to harvest?
Planted on time, broccoli is usually ready from about June 25 to July 20, 60-85 days after transplanting.
When is the last frost in Wisconsin?
On average around May 10, with the first fall frost around September 30 - about 143 frost-free days. Your town may differ by two weeks or more.