When to Plant Potatoes in Illinois: Spring and Fall Dates by Region
What Illinois’s extension calendar says about potatoes, copied region by region, plus the frost record at Chicago O'Hare International Airport, Peoria Greater Peoria Airport, and Springfield Capital Airport.
Updated
Figures checked against their sources on ; next check .
Open University of Illinois Extension’s calendar to the potato line under the heading “Potato” and you find 3 regions, each with its own spring and fall entries. Northern Illinois starts latest, on April 15, while Southern Illinois starts on March 15: 31 days between the two.
What University of Illinois Extension prints for potatoes
The page adds this line for the row: “Sow 12" apart, 2" deep.”
| Region | First planting | Second planting |
|---|---|---|
| Northern Illinois | April 15 to 30 | — |
| Central Illinois | April 1 to 15 | — |
| Southern Illinois | March 15 to 30 | — |
What to know about this source
Illinois Extension splits the state into northern, central and southern Illinois and prints one planting range for each. Southern gardeners can generally start two weeks earlier than central Illinois and harvest for about two weeks longer; northern Illinois can plant about two weeks later than central, the page says.
Do potatoes get an indoor start?
Skip the seed tray. The one source that covers this crop, UNH, plants it directly rather than raising seedlings first.
Potatoes are planted as seed potatoes, not seedlings, so none of the saved seed-starting tables applies; UNH’s timing is counted from the last frost instead.
UNH’s own timing for potatoes is 1 to 2 weeks before the last frost, so Illinois’s printed window and UNH’s rule of thumb can be set side by side.
| Source | What it says |
|---|---|
| University of New Hampshire | Not started indoors; plant seed potatoes 1 to 2 weeks before the last frost |
Where the frost dates fall in Illinois
The dates come straight from NOAA’s frost and freeze normals at the 32°F threshold; the frost dates tool shows earlier and later odds for the same stations.
The last column maps a station to a region only where University of Illinois Extension or its county list settles it.
| Station | Last spring 32°F | First fall 32°F | Region in Illinois’s calendar |
|---|---|---|---|
| Chicago O'Hare International Airport, Illinois | April 16 | October 28 | Northern Illinois |
| Peoria Greater Peoria Airport, Illinois | April 16 | October 23 | Not stated by the source |
| Springfield Capital Airport, Illinois | April 14 | October 20 | Not stated by the source |
| Carbondale Southern Il Airport, Illinois | April 9 | October 22 | Not stated by the source |
| Rockford Greater Rockford Airport, Illinois | April 24 | October 17 | Not stated by the source |
Worked example
Start from Chicago O'Hare International Airport: the station’s median last spring freeze is April 16, and its median first fall freeze is October 28.
Northern Illinois lists April 15 to April 30. Counting from the frost date, that is an opening 1 day before it and a close 14 days after it.
The offsets will shift by a few days with every revision of the normals, so use them as a rough guide to which row to trust and not as a deadline.
Before you rely on these dates
The page tells readers to always confirm dates with the seed packet or plant tag.
A late cold snap after a mild March is the usual way these windows go wrong; keep a sheet or row cover on hand.
Sources (3)
- University of Illinois Extension (Kelly Allsup), When to Plant, Home Vegetable Gardening, updated August 2025 extension.illinois.edu
- NOAA National Centers for Environmental Information, U.S. Climate Normals 1991-2020, annual and seasonal normals (frost/freeze probabilities by station) ncei.noaa.gov
- University of New Hampshire Cooperative Extension, Growing Vegetables: When to Plant Your Vegetable Garden (fact sheet) extension.unh.edu