Iowa planting calendar

When to plant cauliflower in Iowa — sow, transplant & harvest dates

Iowa is mostly USDA zone 5b (range 4b-6a). Dates below are derived from cauliflower's frost tolerance and Iowa's frost window — not generic national averages.

Cauliflower planting timetable for Iowa

Stage	When in Iowa	Anchor
Start seeds indoors	mid-March (March 14)	6 weeks before the last frost (late April)
Transplant outside	mid-April (April 11)	14 days before the last frost (late April)
First harvest (estimate)	early July (July 5)	~85 days from transplant

Dates are state-wide averages for the dominant zone. Local microclimates — elevation, urban heat, coastal moderation — can shift the window by 1-2 weeks. Use the frost-date calculator for a date tuned to your town.

Why Iowa's climate shifts the cauliflower dates

Iowa's last spring frost averages late April and first fall frost early October, which sets the whole planting clock. Iowa has a classic continental prairie climate — cold winters, hot humid summers, and a strong but bounded growing season. Sow early — cauliflower bolt once daytime temperatures hold above 24 °C, so the earlier they go in, the longer the harvest.

More temperature-sensitive than broccoli — optimal growing range is 15–18 °C (60–65 °F); temperatures above 27 °C (80 °F) cause loose, ricey curds, while a sharp frost below −3 °C (27 °F) can damage developing heads. Start indoors 6–8 weeks before last frost and transplant 2–3 weeks before last frost. Blanch white varieties by tying outer leaves over the curd when it reaches golf-ball size, or choose self-blanching types. Succession planting is difficult in spring in hot climates (zones 7+); fall crops from a midsummer sowing are often more reliable.

Frost-risk note

Don't plant before late April — a hard freeze can still set young plants back. In the northern counties near Minnesota (zone 4b) the safe date runs a week or two later.

Regional variation within Iowa

the northern counties near Minnesota (zone 4b) runs roughly 1-2 weeks behind the state average; the southeast along the Mississippi (zone 6a) can plant 1-2 weeks earlier.

Des Moines — USDA zone 5b
Cedar Rapids — USDA zone 5a
Davenport — USDA zone 5b
Sioux City — USDA zone 5a

What else to plant in Iowa around then

The same early window suits peas, lettuce, spinach, and onion sets.

Quick-grow guide

Sun: Full sun — 6+ hours direct.
Soil temperature for germination: 7–24 °C (45–75 °F).
Spacing: 18–24 inches (45–60 cm) between plants.
Days to harvest: ~85 days from planting out.

Frequently asked questions

When is the best time to plant cauliflower in Iowa?

In Iowa (mostly USDA zone 5b), sow cauliflower indoors around mid-March, transplant outdoors mid-April (before the last frost, late April), and harvest from early July. Cauliflower are half-hardy — young plants shrug off a light frost but not a hard freeze, so sowing can start a couple of weeks before the last spring frost.

What USDA zone is Iowa?

Most of Iowa sits in USDA hardiness zone 5b, with the state spanning roughly 4b-6a from the northern counties near Minnesota (zone 4b) to the southeast along the Mississippi (zone 6a). The last spring frost averages late April and the first fall frost early October.

Can you grow cauliflower in Iowa?

Yes. Iowa's dominant zone 5b supports cauliflower — the key is timing. Cauliflower are half-hardy — young plants shrug off a light frost but not a hard freeze, so sowing can start a couple of weeks before the last spring frost.

Does the planting date change across Iowa?

the northern counties near Minnesota (zone 4b) runs roughly 1-2 weeks behind the state average; the southeast along the Mississippi (zone 6a) can plant 1-2 weeks earlier.

What else can I plant in Iowa around the same time?

The same early window suits peas, lettuce, spinach, and onion sets.

Source and methodology

State zone spans from the USDA Plant Hardiness Zone Map (2023); frost-date averages from NOAA Climate Data Online. Hot-state two-season timing cross-checked against the UF/IFAS Florida Gardening Calendar and the University of Arizona Cooperative Extension planting calendar. Curated by the Growli editorial team.