When to plant broccoli in Iowa
Iowa’s average last spring frost is April 25, and the first fall frost typically arrives around October 8 — about 166 frost-free days (USDA zones 4b, 5a, 5b). Broccoli needs 60–85 days to mature, which fits comfortably within Iowa's growing season.
When to plant broccoli in Iowa: the short answer
For a spring planting, plant out Apr 4 – Apr 21, with seeds started indoors Mar 7 – Mar 21. 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 Iowa, step by step
- Start seeds indoors (Mar 7 – Mar 21). 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 4 – Apr 21). 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 Iowa.
- 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 10 – Jul 5). 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 Iowa’s average frost dates. More in the full broccoli growing guide.
Broccoli planting dates by USDA zone in Iowa
Iowa spans USDA zones 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 Iowa ask
When is the best time to plant broccoli in Iowa?
Plant broccoli transplants outdoors in Iowa between April 4 and April 21. That timing is set by Iowa's average last spring frost of April 25.
When should I start broccoli seeds indoors in Iowa?
Start seeds indoors between March 7 and March 21, about 6 weeks before the last frost, so the seedlings are ready to plant out from April 4.
Can I plant broccoli in the fall in Iowa?
Yes. For a fall crop, start transplants between June 29 and July 16, so the crop matures in cool weather before Iowa's first frost around October 8.
When will broccoli planted in Iowa be ready to harvest?
Planted on time, broccoli is usually ready from about June 10 to July 5, 60-85 days after transplanting.
When is the last frost in Iowa?
On average around April 25, with the first fall frost around October 8 - about 166 frost-free days. Your town may differ by two weeks or more.