FrostCal

When to Plant Onions in Illinois

In a typical Illinois location, start seeds indoors Feb 9 – Feb 23, then transplant outdoors Mar 23 – Apr 6. Across the state, the outdoor planting window starts as early as Mar 4 in Granite City and as late as Apr 3 in Roscoe.

Method Start indoors, then transplant
Days to maturity 90–120 days

Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings.

Onions Planting Dates by City

CityStart indoorsTransplant
ChicagoJan 30 – Feb 13Mar 13 – Mar 27
AuroraFeb 8 – Feb 22Mar 22 – Apr 5
RockfordFeb 13 – Feb 27Mar 27 – Apr 10
JolietFeb 8 – Feb 22Mar 22 – Apr 5
NapervilleFeb 17 – Mar 3Mar 31 – Apr 14
PeoriaFeb 5 – Feb 19Mar 19 – Apr 2
SpringfieldFeb 4 – Feb 18Mar 18 – Apr 1
North PeoriaFeb 5 – Feb 19Mar 19 – Apr 2
ElginFeb 15 – Mar 1Mar 29 – Apr 12
WaukeganFeb 19 – Mar 5Apr 2 – Apr 16
ChampaignFeb 4 – Feb 18Mar 18 – Apr 1
CiceroJan 31 – Feb 14Mar 14 – Mar 28
BloomingtonFeb 10 – Feb 24Mar 24 – Apr 7
Arlington HeightsFeb 8 – Feb 22Mar 22 – Apr 5
EvanstonFeb 15 – Mar 1Mar 29 – Apr 12
SchaumburgFeb 19 – Mar 5Apr 2 – Apr 16
BolingbrookFeb 9 – Feb 23Mar 23 – Apr 6
DecaturFeb 3 – Feb 17Mar 17 – Mar 31
PalatineFeb 14 – Feb 28Mar 28 – Apr 11
SkokieFeb 15 – Mar 1Mar 29 – Apr 12
Des PlainesFeb 5 – Feb 19Mar 19 – Apr 2
Orland ParkFeb 8 – Feb 22Mar 22 – Apr 5
Tinley ParkFeb 12 – Feb 26Mar 26 – Apr 9
Oak LawnJan 30 – Feb 13Mar 13 – Mar 27
BerwynJan 31 – Feb 14Mar 14 – Mar 28
Mount ProspectFeb 8 – Feb 22Mar 22 – Apr 5
NormalFeb 14 – Feb 28Mar 28 – Apr 11
WheatonFeb 17 – Mar 3Mar 31 – Apr 14
Oak ParkJan 31 – Feb 14Mar 14 – Mar 28
Hoffman EstatesFeb 19 – Mar 5Apr 2 – Apr 16

Showing the 30 most populous of 242 Illinois cities. Dates are estimates from each city's NOAA frost normals and university extension timing guidelines. See all Illinois cities.

Frequently Asked Questions

When should I plant onions in Illinois?

In a typical Illinois location, start seeds indoors Feb 9 – Feb 23, then transplant outdoors Mar 23 – Apr 6. Across the state, the outdoor planting window starts as early as Mar 4 in Granite City and as late as Apr 3 in Roscoe.

When is the last frost in Illinois?

The average last spring frost in Illinois ranges from April 1 in Granite City to May 1 in Roscoe, based on NOAA 1991–2020 climate normals.

How long do onions take to grow?

Onions typically take 90–120 days from planting to harvest. Start seeds indoors 8-10 weeks before last frost (or use sets/transplants); set out 2-4 weeks before last frost, very cold-tolerant as seedlings.

Other Crops in Illinois

When to plant onions in other states

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