When to Plant Onions in Indiana
The backbone of the kitchen garden. Choose short-day, intermediate, or long-day varieties based on your latitude.
The Short Answer
Indiana Frost Dates
Your planting dates depend on which part of Indiana you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Indiana | 5b, 6a | Apr 25 - May 10 | Oct 1 - Oct 15 |
| Central Indiana | 6a, 6b | Apr 15 - May 1 | Oct 10 - Oct 25 |
| Southern Indiana | 6b | Apr 10 - Apr 25 | Oct 15 - Nov 1 |
Onions Planting Schedule for Indiana
Northern Indiana (Zones 5b, 6a)
Average last frost: Apr 25 - May 10 · Average first frost: Oct 1 - Oct 15
Central Indiana (Zones 6a, 6b)
Average last frost: Apr 15 - May 1 · Average first frost: Oct 10 - Oct 25
Southern Indiana (Zones 6b)
Average last frost: Apr 10 - Apr 25 · Average first frost: Oct 15 - Nov 1
Growing Onions in Indiana
Onions in Indiana's Climate
Long-day onions are your type. Plant sets or transplants as soon as ground can be worked in spring. For the largest bulbs, start from seed indoors 10-12 weeks before last frost. Your June day length (15+ hours) triggers proper bulbing. Cure in a warm, dry location for 2-3 weeks before storage.
Soil Considerations for Indiana
Clay-heavy soils common statewide. Rich but can have drainage issues. Raised beds help with heavy clay. Loose, well-drained soil is especially important for onions since the edible portion grows underground. If your soil is heavy clay, consider raised beds.
Indiana Climate & Growing Season
Four seasons. Hot, humid summers. Adequate rainfall for most crops. Occasional late spring frosts catch gardeners off guard. Onions can handle frost well, which is an advantage in Indiana's climate. You can push planting dates earlier in spring and extend into fall.
Growing season length varies across Indiana: Northern Indiana (5b, 6a) has a last frost around Apr 25 - May 10, while Southern Indiana (6b) sees frost end around Apr 10 - Apr 25. This difference matters for onions — but onions handle frost well, so the timing difference is less critical.
Growing Tips
Day length triggers bulbing. Northern gardeners need long-day varieties. Southern gardeners need short-day varieties.
Companion Planting
Plant onions alongside these companions for better growth:
Keep onions away from:
The Bottom Line
Last reviewed: March 29, 2026