What Planting Zones Are in Iowa?
Iowa spans USDA hardiness zones 4b to 6a, where the average coldest winter night ranges from −25 °F to −5 °F (−31.7 °C to −20.6 °C). Zone 5a covers the most ZIP codes, 54%, and zones 5a to 5b together cover 96% of the state.
Bars show each zone's share of the 1,042 Iowa ZIP codes in the official 2023 USDA ZIP code table; select a zone for its temperatures and hardy plants.
What Hardiness Zone Are Iowa Cities In?
Des Moines is in zone 5b, Cedar Rapids is in zone 5b, Davenport is in zone 5b and Sioux City is in zone 5a. The table lists the zone, winter low and average frost dates for 18 Iowa cities, using the ZIP code nearest each city center.
| City | ZIP | Zone | Winter low | Last frost | First frost |
|---|---|---|---|---|---|
| Des Moines | 50309 | 5b | −15 °F to −10 °F | Apr 18 | Oct 20 |
| Cedar Rapids | 52401 | 5b | −15 °F to −10 °F | Apr 28 | Oct 12 |
| Davenport | 52806 | 5b | −15 °F to −10 °F | Apr 23 | Oct 15 |
| Sioux City | 51101 | 5a | −20 °F to −15 °F | Apr 29 | Oct 7 |
| Ankeny | 50023 | 5b | −15 °F to −10 °F | Apr 23 | Oct 15 |
| Iowa City | 52242 | 5b | −15 °F to −10 °F | Apr 21 | Oct 18 |
| West Des Moines | 50265 | 5b | −15 °F to −10 °F | Apr 18 | Oct 20 |
| Ames | 50012 | 5b | −15 °F to −10 °F | Apr 26 | Oct 8 |
| Waterloo | 50702 | 5a | −20 °F to −15 °F | Apr 27 | Oct 10 |
| Council Bluffs | 51501 | 5b | −15 °F to −10 °F | Apr 18 | Oct 21 |
| Dubuque | 52001 | 5a | −20 °F to −15 °F | Apr 19 | Oct 21 |
| Marshalltown | 50158 | 5a | −20 °F to −15 °F | Apr 28 | Oct 7 |
| Mason City | 50401 | 5a | −20 °F to −15 °F | Apr 29 | Oct 7 |
| Ottumwa | 52501 | 5b | −15 °F to −10 °F | Apr 23 | Oct 14 |
| Fort Dodge | 50501 | 5a | −20 °F to −15 °F | Apr 28 | Oct 8 |
| Clinton | 52732 | 5b | −15 °F to −10 °F | Apr 13 | Oct 26 |
| Burlington | 52601 | 6a | −10 °F to −5 °F | Apr 15 | Oct 20 |
| Muscatine | 52761 | 5b | −15 °F to −10 °F | Apr 24 | Oct 14 |
Zone: 2023 USDA ZIP code table for the ZIP code nearest each city's Census center point. Frost dates: 50% (median) dates from the nearest NOAA station, 1991–2020 normals. Cities: the largest Iowa places by 2024 Census population estimates, spread across the state, plus the largest place in each common zone. Large cities can span two half zones.
Which Parts of Iowa Are in Each Zone?
Zone 4b, the coldest Iowa zone, covers 2% of ZIP codes around Cresco, Sibley and Elkader. Zone 6a, the warmest, covers 3% around Burlington, Fort Madison and Keokuk. The table lists the largest places in every zone.
| Zone | Avg. coldest night | Share of ZIPs | Largest places in this zone |
|---|---|---|---|
| Zone 4b | −25 °F to −20 °F | 2% (17) | Cresco, Sibley, Elkader, Strawberry Point |
| Zone 5a | −20 °F to −15 °F | 54% (563) | Sioux City, Waterloo, Dubuque, Marion |
| Zone 5b | −15 °F to −10 °F | 42% (433) | Des Moines, Cedar Rapids, Davenport, Ankeny |
| Zone 6a | −10 °F to −5 °F | 3% (29) | Burlington, Fort Madison, Keokuk, Glenwood |
Places: incorporated places with 1,000+ residents, assigned the zone of the ZIP code nearest their Census center point.
What Do the Hardiness Zones Mean for Iowa Gardeners?
A Iowa gardener in zone 6a sees winter lows about 15 °F milder than one in zone 4b, so a shrub or perennial that thrives in one part of the state can die in another. Choose plants rated to your own ZIP code's zone or colder.
Hardiness zones follow latitude, elevation and large bodies of water rather than state lines. Higher ground and inland valleys that trap cold air usually sit in colder half zones, while cities, coasts and large lakes moderate winter lows. Within Iowa, a plant labelled “zones 5–6” survives winter in at least 96% of ZIP codes, but plants at the edge of their range benefit from mulch and a sheltered spot. Enter a ZIP code in the USDA hardiness zone finder by ZIP code to check your exact half zone before buying perennials.
A zone describes winter cold only. Summer heat, humidity, rainfall and soil decide whether a cold-hardy plant thrives, and planting dates for vegetables follow frost dates, not zones: two Iowa towns in the same zone can have last frosts weeks apart.
What Plants Grow Well Across Iowa?
200 plants in PlantoScan's catalogue are hardy in every zone from 5a to 5b, the zones that cover 96% of Iowa ZIP codes. Popular examples include hydrangea, peony and daisy.
Hydrangea
Hydrangea macrophylla
Zone 5 – 9
AI generated
Peony
Paeonia lactiflora
Zone 3 – 8
AI generated
- DaisyBellis perennisPlantoScan
Daisy
Bellis perennis
Zone 4a – 8b
Chrysanthemum
Chrysanthemum morifolium
Zone 5a – 9b
PlantoscanAI generated
Poppy
Papaver somniferum
Zone 3a – 9b
AI generated
Carnation
Dianthus caryophyllus
Zone 5a – 9b
AI generated
Daffodil
Narcissus poeticus
Zone 3 – 8
AI generated
Arugula
Eruca sativa
Zone 5a – 10b
AI generated
Alfalfa
Medicago sativa
Zone 3a – 10a
AI generated
Hardiness ranges come from PlantoScan's plant database; gardeners in Iowa's colder or warmer edge zones should check each plant's full range.
When Is the Last Frost in Iowa?
Across most Iowa ZIP codes, the average last spring frost falls between April 19 and May 3, from April 13 in Clinton to April 29 in Mason City. Tender vegetables such as tomatoes go out 1 to 2 weeks after the local date.
The last and first frost dates for Iowa cities include the safer 90% planting date, the fall frost date, growing season length and a tomato planting table for each city.
Frequently Asked Questions
- What planting zone is Iowa?
- Iowa spans USDA hardiness zones 4b to 6a on the 2023 USDA Plant Hardiness Zone Map. Zone 5a is the most common, covering 54% of the state's 1,042 ZIP codes, and zones 5a to 5b together cover 96%.
- What hardiness zone is Des Moines, Iowa?
- Des Moines is in USDA hardiness zone 5b (ZIP 50309), where the average coldest winter night reaches −15 °F to −10 °F. Its average last spring frost is April 18 and its first fall frost October 20.
- What hardiness zone is Cedar Rapids, Iowa?
- Cedar Rapids is in USDA hardiness zone 5b (ZIP 52401), where the average coldest winter night reaches −15 °F to −10 °F. Its average last spring frost is April 28 and its first fall frost October 12.
- What hardiness zone is Davenport, Iowa?
- Davenport is in USDA hardiness zone 5b (ZIP 52806), where the average coldest winter night reaches −15 °F to −10 °F. Its average last spring frost is April 23 and its first fall frost October 15.
- What is the coldest hardiness zone in Iowa?
- Zone 4b (−25 °F to −20 °F) is the coldest zone in Iowa, found in 17 ZIP codes around Cresco and Sibley. The warmest is zone 6a (−10 °F to −5 °F), around Burlington and Fort Madison.
Zones: 2023 USDA Plant Hardiness Zone Map ZIP code table, USDA Agricultural Research Service and the PRISM Climate Group, Oregon State University, used without changes. Frost dates: NOAA National Centers for Environmental Information, 1991–2020 U.S. Climate Normals. City locations and populations: U.S. Census Bureau Gazetteer files and Vintage 2024 population estimates. PlantoScan is not affiliated with or endorsed by these agencies.