When to plant onions in Nebraska
Nebraska’s average last spring frost is April 30, and the first fall frost typically arrives around October 5 — about 158 frost-free days (USDA zones 4b, 5a, 5b). Onion needs 90–120 days to mature, which fits comfortably within Nebraska's growing season.
When to plant onions in Nebraska: the short answer
For a spring planting, plant out Apr 2 – Apr 19, with seeds started indoors Feb 12 – Feb 26. 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 Nebraska, step by step
- Start seeds indoors (Feb 12 – Feb 26). 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 (Apr 2 – Apr 19). 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 Nebraska.
- 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 Jul 8 – Aug 7). 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 Nebraska’s average frost dates. More in the full onion growing guide.
Onion planting dates by USDA zone in Nebraska
Nebraska spans USDA zones 4b, 5a, 5b. 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 |
|---|---|---|
| Nebraska (this page) | April 30 | Apr 2 – Apr 19 |
| North Dakota | May 15 | Apr 17 – May 4 |
| South Dakota | May 10 | Apr 12 – Apr 29 |
| Kansas | April 15 | Mar 18 – Apr 4 |
| Oklahoma | April 1 | Mar 4 – Mar 21 |
Questions gardeners in Nebraska ask
When is the best time to plant onions in Nebraska?
Plant onion transplants outdoors in Nebraska between April 2 and April 19. That timing is set by Nebraska's average last spring frost of April 30.
When should I start onion seeds indoors in Nebraska?
Start seeds indoors between February 12 and February 26, about 10 weeks before the last frost, so the seedlings are ready to plant out from April 2.
When will onions planted in Nebraska be ready to harvest?
Planted on time, onions are usually ready from about July 8 to August 7, 90-120 days after transplanting.
When is the last frost in Nebraska?
On average around April 30, with the first fall frost around October 5 - about 158 frost-free days. Your town may differ by two weeks or more.