When to Plant Onions in Missouri
The backbone of the kitchen garden. Choose short-day, intermediate, or long-day varieties based on your latitude.
The Short Answer
Missouri Frost Dates
Your planting dates depend on which part of Missouri you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Northern Missouri | 5b, 6a | Apr 20 - May 5 | Oct 1 - Oct 15 |
| Central Missouri | 6a, 6b | Apr 10 - Apr 25 | Oct 10 - Oct 25 |
| Southern Missouri | 6b, 7a | Apr 1 - Apr 15 | Oct 15 - Nov 1 |
Onions Planting Schedule for Missouri
Northern Missouri (Zones 5b, 6a)
Average last frost: Apr 20 - May 5 · Average first frost: Oct 1 - Oct 15
Central Missouri (Zones 6a, 6b)
Average last frost: Apr 10 - Apr 25 · Average first frost: Oct 10 - Oct 25
Southern Missouri (Zones 6b, 7a)
Average last frost: Apr 1 - Apr 15 · Average first frost: Oct 15 - Nov 1
Growing Onions in Missouri
Onions in Missouri'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 Missouri
Rich loess soils along Missouri River. Rocky Ozark soils in south. Heavy clay common. Generally fertile. Loose, well-drained soil is especially important for onions since the edible portion grows underground. If your soil is heavy clay, consider raised beds.
Missouri Climate & Growing Season
Continental climate. Hot, humid summers. Four seasons. Good growing season in most of state. Onions can handle frost well, which is an advantage in Missouri's climate. You can push planting dates earlier in spring and extend into fall.
Growing season length varies across Missouri: Northern Missouri (5b, 6a) has a last frost around Apr 20 - May 5, while Southern Missouri (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