When to Plant Onions in South Carolina
The backbone of the kitchen garden. Choose short-day, intermediate, or long-day varieties based on your latitude.
The Short Answer
South Carolina Frost Dates
Your planting dates depend on which part of South Carolina you're in. Here are the frost date ranges by region:
| Region | Zones | Last Frost (Spring) | First Frost (Fall) |
|---|---|---|---|
| Upstate | 7a, 7b | Mar 25 - Apr 10 | Oct 20 - Nov 5 |
| Midlands | 7b, 8a | Mar 15 - Apr 1 | Nov 1 - Nov 15 |
| Coastal | 8a, 8b, 9a | Feb 25 - Mar 15 | Nov 10 - Dec 1 |
Onions Planting Schedule for South Carolina
Upstate (Zones 7a, 7b)
Average last frost: Mar 25 - Apr 10 · Average first frost: Oct 20 - Nov 5
Midlands (Zones 7b, 8a)
Average last frost: Mar 15 - Apr 1 · Average first frost: Nov 1 - Nov 15
Coastal (Zones 8a, 8b, 9a)
Average last frost: Feb 25 - Mar 15 · Average first frost: Nov 10 - Dec 1
Growing Onions in South Carolina
Onions in South Carolina's Climate
You straddle the day-length divide. Southern areas need short-day varieties (plant in fall for spring harvest), northern areas can use intermediate-day types. The single most important decision for onion success in your zone is choosing the right day-length type — the wrong one produces scallions instead of bulbs regardless of how well you grow them.
Soil Considerations for South Carolina
Red clay in Piedmont. Sandy soils on coast. Acidic throughout. Rich alluvial soils in river valleys. Loose, well-drained soil is especially important for onions since the edible portion grows underground. If your soil is heavy clay, consider raised beds.
South Carolina Climate & Growing Season
Long, hot growing season. Subtropical on coast. Two main planting seasons. Summer heat can stress cool-season crops. Onions can handle frost well, which is an advantage in South Carolina's climate. You can push planting dates earlier in spring and extend into fall.
Growing season length varies across South Carolina: Upstate (7a, 7b) has a last frost around Mar 25 - Apr 10, while Coastal (8a, 8b, 9a) sees frost end around Feb 25 - Mar 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