When to plant onions in zone 5a
In zone 5a, where the last spring frost typically comes around May 3, start onions indoors January 11 to February 22 and plant out April 5 to 19.
The zone 5a schedule for onions
- Start seeds indoors
- January 11 to February 22
- Plant out
- April 5 to 19
- Sow outdoors
- March 22 to April 5
From the median frost dates of the NOAA stations assigned to the 2,200 ZIP codes in zone 5a, and the timing recommended by Cooperative Extension guides for onions.
Dates before the last frost assume the soil has thawed and is dry enough to work: a squeezed handful crumbles instead of sticking. After a late or wet spring, wait for that even if the date has passed.
Frost risk in zone 5a
Zones are based on winter cold, not on frost dates, so the last spring frost varies a lot within a zone. Across zone 5a, the typical last frost ranges from about April 27 in the earliest tenth of ZIP codes to May 21 in the latest tenth, and the first fall frost from September 25 to October 13. For a typical place in the zone:
- April 20Risky: a later frost happens in 9 years out of 10
- May 3Typical: frost after this date in half of years
- May 17Safe: a later frost only 1 year in 10
Your dates for onions
Set your ZIP code at the top of the page and we will work out when to plant onions where you live, from the frost records of the nearest NOAA weather station. Your ZIP code is remembered on this device only.
Onions in zone 5a cities
| City | Typical last frost | Start indoors | Plant out |
|---|---|---|---|
| Minneapolis, MN | Apr 23 | Jan 1 to Feb 12 | Mar 26 to Apr 9 |
| St. Paul, MN | Apr 23 | Jan 1 to Feb 12 | Mar 26 to Apr 9 |
| Anchorage, AK | May 5 | Jan 13 to Feb 24 | Apr 7 to 21 |
| Sioux Falls, SD | May 1 | Jan 9 to Feb 20 | Apr 3 to 17 |
| Cedar Rapids, IA | Apr 28 | Jan 6 to Feb 17 | Mar 31 to Apr 14 |
| Billings, MT | May 10 | Jan 18 to Mar 1 | Apr 12 to 26 |
| Bloomington, MN | Apr 23 | Jan 1 to Feb 12 | Mar 26 to Apr 9 |
| Sioux City, IA | Apr 29 | Jan 7 to Feb 18 | Apr 1 to 15 |
| Brooklyn Park, MN | Apr 30 | Jan 8 to Feb 19 | Apr 2 to 16 |
| Woodbury, MN | Apr 24 | Jan 2 to Feb 13 | Mar 27 to Apr 10 |
| Plymouth, MN | Apr 29 | Jan 7 to Feb 18 | Apr 1 to 15 |
| Blaine, MN | Apr 30 | Jan 8 to Feb 19 | Apr 2 to 16 |
How to grow onionsAll zonesOnions in zone 4bOnions in zone 5bAbout zone 5a
Sources
- How to Grow Onions in Your Garden · Utah State University Extension
- Growing Onions in a Home Garden · University of Maryland Extension
- How to Start Onions and Leeks from Seeds · University of Maryland Extension (Maryland Grows)
- Growing Onions - Sets, Plants or Seeds? · Nebraska Extension in Lancaster County
- How to Grow Onions · University of Vermont Extension
- Onions (food fact sheet) · Montana State University Extension
- Planting the Garden · University of Vermont Extension
- Rhode Island Planting Calendar for Fruits and Vegetables · University of Rhode Island Cooperative Extension
- Soil temperature conditions for vegetable seed germination · Oregon State University Extension Service
- Onion, Leek, Shallot, & Garlic (HGIC) · Clemson Cooperative Extension Home & Garden Information Center
- Allium cepa (Plant Toolbox) · NC State Extension
- SP 103/VH021: Florida Vegetable Gardening Guide · University of Florida IFAS Extension
- Onions and Shallots · University of Florida IFAS Gardening Solutions
- Onions (Easy Gardening) · Texas A&M AgriLife Extension
- Vegetable Planting Calendar for Maricopa County (AZ1005) · University of Arizona Cooperative Extension