When to plant onions in North Carolina
North Carolina’s average last spring frost is April 5, and the first fall frost typically arrives around October 25 — about 203 frost-free days (USDA zones 5b, 6a, 6b, 7a, 7b, 8a, 8b). Onion needs 90–120 days to mature, which fits comfortably within North Carolina's growing season.
North Carolina covers a wide range of climates, so your exact frost dates may differ from the state average by two weeks or more. For dates tuned to your town, use the calendar generator.
When to plant onions in North Carolina: the short answer
For a spring planting, plant out Mar 8 – Mar 25, with seeds started indoors Jan 18 – Feb 1. Seeds germinate in soil from 40 to 90°F.
Windows are ~1–2 week bands around each date. Frost dates are a statewide average from NOAA/NCEI normals; your town may differ by two weeks or more. Calendar year 2026.
How to grow onions in North Carolina, step by step
- Start seeds indoors (Jan 18 – Feb 1). Sow seeds ½ inch deep in seed-starting mix under bright light. They take 7-14 days to sprout, fastest in soil around 70°F. Harden seedlings off for a week before they go outside.
- Prepare the bed. They need at least six to eight hours of direct sun a day and loose soil at least 12 inches deep, with a pH between 6.0 and 7.0. Dig in compost before planting.
- Plant out (Mar 8 – Mar 25). Space plants about 4 inches apart in rows 12 inches apart. It handles frost well, so it can go out before the last frost date. As a cool-season crop it does best before summer heat arrives in North Carolina.
- Water and feed. Give it steady, even moisture, about an inch of water a week from rain or the hose.
- Watch for pests and problems. Pests: onion maggot, onion thrips. Diseases and disorders: downy mildew, white rot, neck rot, purple blotch.
- Harvest (from about Jun 13 – Jul 13). Onion takes 90-120 days to reach harvest. Match the day-length type to your latitude: long-day onions for the north, short-day for the south, day-neutral anywhere. Bulbing is triggered by day length, not calendar date.
Figures come from our crop data; dates use North Carolina’s average frost dates. More in the full onion growing guide.
Onion planting dates by USDA zone in North Carolina
North Carolina spans USDA zones 5b, 6a, 6b, 7a, 7b, 8a, 8b. Colder zones, usually higher or further inland, have a later last spring frost and an earlier first fall frost than the state average, so the onion dates shift with them.
When to plant onions in nearby states
| State | Last frost | Plant out |
|---|---|---|
| North Carolina (this page) | April 5 | Mar 8 – Mar 25 |
| South Carolina | March 25 | Feb 25 – Mar 14 |
| Georgia | March 25 | Feb 25 – Mar 14 |
| Tennessee | April 10 | Mar 13 – Mar 30 |
| Kentucky | April 18 | Mar 21 – Apr 7 |
Questions gardeners in North Carolina ask
When is the best time to plant onions in North Carolina?
Plant onion transplants outdoors in North Carolina between March 8 and March 25. That timing is set by North Carolina's average last spring frost of April 5; North Carolina spans several climates, so cooler and higher parts of the state run later.
When should I start onion seeds indoors in North Carolina?
Start seeds indoors between January 18 and February 1, about 10 weeks before the last frost, so the seedlings are ready to plant out from March 8.
When will onions planted in North Carolina be ready to harvest?
Planted on time, onions are usually ready from about June 13 to July 13, 90-120 days after transplanting.
When is the last frost in North Carolina?
On average around April 5, with the first fall frost around October 25 - about 203 frost-free days. Your town may differ by two weeks or more.