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When to plant / Illinois

When to plant onions (green) sets in Illinois

The planting chart is divided into Northern Illinois, Central Illinois, and Southern Illinois. Median dates for the last 32-degree freeze on the same page: Northern Illinois April 8-29; Central Illinois April 8-15; Southern Illinois April 1-8. The page also says southern Illinois can generally start crops two weeks earlier than central Illinois and northern Illinois about two weeks later; the crop rows below are the chart dates, not a recalculation of that sentence.

Source: University of Illinois Extension, When to Plant, retrieved 2026-10-10.

How this page reads that source: Illinois Fruit and Vegetable Planting Dates chart: north: April 9 to May 15; central: March 25 to May 1; south: March 11 to April 15.

North

  • April 9 to May 15 (April 9–May 15).

Central

  • March 25 to May 1 (March 25–May 1).

South

  • March 11 to April 15 (March 11–April 15).

City frost pages in Illinois are listed on Illinois.