When to plant cauliflower 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). Cauliflower needs 60–90 days to mature, which fits comfortably within Iowa's growing season.
When to plant cauliflower 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 cauliflower 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 7.5. 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. It needs plenty of water; keep the soil evenly moist and never let it dry out.
- Watch for pests and problems. Pests: cabbage worm, cabbage looper, aphids, cabbage root maggot. Diseases and disorders: clubroot, black rot, downy mildew.
- Harvest (from about Jun 10 – Jul 10). Cauliflower takes 60-90 days to reach harvest. The fussiest brassica - any check from cold, heat, or drought ruins the head. Fall crops are far more reliable than spring. Blanch white types by tying leaves over the curd.
Figures come from our crop data; dates use Iowa’s average frost dates. More in the full cauliflower growing guide.
Cauliflower 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 cauliflower dates shift with them.
When to plant cauliflower in nearby states
Questions gardeners in Iowa ask
When is the best time to plant cauliflower in Iowa?
Plant cauliflower 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 cauliflower 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 cauliflower 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 cauliflower planted in Iowa be ready to harvest?
Planted on time, cauliflower is usually ready from about June 10 to July 10, 60-90 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.