When to Plant Onions in Kansas
The backbone of the kitchen garden. Choose short-day, intermediate, or long-day varieties based on your latitude.
The Short Answer
Kansas Frost Dates
Your planting dates depend on which part of Kansas you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Kansas | 5b, 6a | Apr 20 - May 5 | Oct 1 - Oct 15 |
| Central Kansas | 6a, 6b | Apr 10 - Apr 25 | Oct 10 - Oct 25 |
| Southern Kansas | 6b, 7a | Apr 1 - Apr 15 | Oct 15 - Nov 1 |
Onions Planting Schedule for Kansas
Northern Kansas (Zones 5b, 6a)
Average last frost: Apr 20 - May 5 · Average first frost: Oct 1 - Oct 15
Central Kansas (Zones 6a, 6b)
Average last frost: Apr 10 - Apr 25 · Average first frost: Oct 10 - Oct 25
Southern Kansas (Zones 6b, 7a)
Average last frost: Apr 1 - Apr 15 · Average first frost: Oct 15 - Nov 1
Growing Onions in Kansas
Onions in Kansas'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 Kansas
Prairie soils in east — rich and deep. More alkaline and thinner soils in west. Wind erosion can be an issue. Loose, well-drained soil is especially important for onions since the edible portion grows underground. If your soil is heavy clay, consider raised beds.
Kansas Climate & Growing Season
Hot summers with strong winds. Severe thunderstorms and hail risk. Drier in the west. Good growing conditions for heat-loving crops. Onions can handle frost well, which is an advantage in Kansas's climate. You can push planting dates earlier in spring and extend into fall.
Growing season length varies across Kansas: Northern Kansas (5b, 6a) has a last frost around Apr 20 - May 5, while Southern Kansas (6b, 7a) sees frost end around Apr 1 - Apr 15. 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