Iowa planting calendar

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

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

Kale 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	late March (March 28)	28 days before the last frost (late April)
First harvest (estimate)	late May (May 27)	~60 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 kale 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 — kale bolt once daytime temperatures hold above 24 °C, so the earlier they go in, the longer the harvest.

Kale is among the hardiest brassicas, surviving temperatures as low as −12 °C (10 °F) in protected conditions; frost sweetens the leaves by converting starches to sugars. Transplant or direct-sow 4–6 weeks before last spring frost; can also be direct-sown. For fall/winter harvest, direct-sow or transplant 6–8 weeks before first autumn frost. Avoid planting when temperatures consistently exceed 27 °C (80 °F) as heat reduces palatability and increases bitterness. Harvest outer leaves continuously to extend production; the plant does not form a head and can be harvested over many months.

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 to part shade — 4–6+ hours direct.
Soil temperature for germination: 7–29 °C (45–85 °F).
Spacing: 12–18 inches (30–45 cm) between plants.
Days to harvest: ~60 days from planting out.

Frequently asked questions

When is the best time to plant kale in Iowa?

In Iowa (mostly USDA zone 5b), sow kale indoors around mid-March, transplant outdoors late March (before the last frost, late April), and harvest from late May. Kale are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

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 kale in Iowa?

Yes. Iowa's dominant zone 5b supports kale — the key is timing. Kale are cold-hardy — they tolerate frost and actively prefer cool weather, so they go in well before the last spring frost and bolt in summer heat.

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.