Ankeny, Iowa: planting zone & frost dates
Ankeny is in USDA plant hardiness zone 5b, where the average coldest winter night reaches -15 to -10°F (-26.1 to -23.3°C). The typical last spring frost is around Apr 29 and the first fall frost around Oct 9.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 6 | Sep 30 |
| Typical planning date (30% risk) | Apr 29 | Oct 9 |
| Median (50%) | Apr 23 | Oct 15 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station ANKENY, IA (USC00130241), 2.5 mi (4.1 km) from the city center and 3 ft lower than the city center (-1 m). Record used for the 1991–2020 normals: 27 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Ankeny
All 2 ZIP codes covering Ankeny are in zone 5b.
Vegetable planting calendar for Ankeny
Dates are counted from the 30%-risk frost dates above (last frost Apr 29, first frost Oct 9). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Mar 4 – Mar 18 | May 6 – May 20 | — | — |
| Pepper | Feb 18 – Mar 4 | May 13 – May 27 | — | — |
| Lettuce | Mar 18 – Apr 1 | Apr 15 – May 6 | Apr 1 – May 13 | Jul 31 – Aug 28 |
| Green Beans | — | — | May 6 – Jun 10 | Jul 17 – Jul 31 |
| Sweet Corn | — | — | May 6 – Jun 3 | — |
| Zucchini & Summer Squash | Apr 1 – Apr 8 | May 6 – May 20 | May 6 – May 27 | Jul 17 – Jul 31 |
| Cucumber | Apr 1 – Apr 8 | May 13 – May 20 | May 6 – May 27 | Jul 17 – Jul 31 |
| Carrot | — | — | Apr 8 – May 13 | Jul 17 – Jul 31 |
| Onion | Feb 4 – Feb 18 | Apr 1 – Apr 15 | — | — |
| Potato | — | Apr 1 – Apr 22 | — | — |
| Basil | Mar 18 – Apr 1 | May 13 – May 27 | May 13 – Jun 3 | — |
| Spinach | — | — | Mar 18 – Apr 15 | Aug 14 – Sep 11 |
| Kale | Mar 4 – Mar 18 | Apr 1 – Apr 22 | Apr 1 – Apr 22 | Jul 31 – Aug 28 |
| Broccoli | Mar 4 – Mar 18 | Apr 15 – May 6 | — | Jul 17 – Jul 31 |
| Peas | — | — | Mar 18 – Apr 8 | Jul 31 – Aug 14 |
| Eggplant | Feb 18 – Mar 4 | May 13 – May 27 | — | — |
| Cabbage | Mar 4 – Mar 18 | Apr 1 – Apr 15 | — | Jul 17 – Jul 31 |
| Radish | — | — | Mar 25 – May 13 | Aug 28 – Sep 25 |
| Strawberry | — | Apr 1 – Apr 22 | — | — |
| Beets | — | — | Apr 8 – May 20 | Jul 31 – Aug 14 |
Nearby cities in Iowa
- Des Moines — zone 5b, last frost Apr 24, first frost Oct 14
- Cedar Rapids — zone 5a, last frost May 3, first frost Oct 5
- Iowa City — zone 5b, last frost Apr 28, first frost Oct 13
- Sioux City — zone 5a, last frost May 4, first frost Oct 1
- Davenport — zone 5b, last frost Apr 24, first frost Oct 17
More: all Iowa cities · other zone 5b cities: Madison, WI, Des Moines, IA, Aurora, IL, Fort Collins, CO, Naperville, IL, Rockford, IL, Elgin, IL, Greeley, CO
Ankeny gardening questions
When is the last frost in Ankeny, IA?
Plan around Apr 29. At NOAA's Ankeny, IA station, 2.5 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Apr 23, and after May 6 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 13. The last frost is fairly predictable here: only 28 days separate the 90% and 10% dates (median for cities on this site: 36 days).
When should I plant tomatoes in Ankeny, IA?
Start seeds indoors Mar 4 – Mar 18 and set transplants outside May 6 – May 20, once nights stay above 50°F and the soil is near 60°F. That leaves 163 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Ankeny?
About 173 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 154 days, and in 1 year in 10 it runs 193 days or more. In fall there is a 10% chance of frost by Sep 30 and a 30% chance by Oct 9. That ranks 4th longest of 6 Iowa cities on this site.
When should I plant a fall garden in Ankeny?
Count back from the first fall frost (Oct 9): transplant broccoli Jul 17 – Jul 31; sow kale Jul 31 – Aug 28; sow lettuce Jul 31 – Aug 28; sow radishes Aug 28 – Sep 25. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 25. How the math works: succession and fall planting.
Did Ankeny's hardiness zone change on the 2023 map?
Yes. Most of Ankeny was zone 5a on the 2012 map and is zone 5b on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
How does Ankeny compare with Des Moines, IA?
Both are in zone 5b. The typical last spring frost in Ankeny (Apr 29) comes about 5 days later than in Des Moines, IA (Apr 24), 11 miles away, and the first fall frost is Oct 9 versus Oct 14. Ankeny sits about 186 ft higher, which explains part of the gap. The two cities use different NOAA stations.