When to plant onions in zone 6a
In zone 6a, where the last spring frost typically comes around April 29, start onions indoors January 7 to February 18 and plant out April 1 to 15.
The zone 6a schedule for onions
- Start seeds indoors
- January 7 to February 18
- Plant out
- April 1 to 15
- Sow outdoors
- March 18 to April 1
From the median frost dates of the NOAA stations assigned to the 4,514 ZIP codes in zone 6a, 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 6a
Zones are based on winter cold, not on frost dates, so the last spring frost varies a lot within a zone. Across zone 6a, the typical last frost ranges from about April 16 in the earliest tenth of ZIP codes to May 11 in the latest tenth, and the first fall frost from October 4 to October 24. For a typical place in the zone:
- April 16Risky: a later frost happens in 9 years out of 10
- April 29Typical: frost after this date in half of years
- May 14Safe: 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 6a cities
| City | Typical last frost | Start indoors | Plant out |
|---|---|---|---|
| Chicago, IL | Apr 11 | Dec 20 to Jan 31 | Mar 14 to 28 |
| Indianapolis city, IN | Apr 15 | Dec 24 to Feb 4 | Mar 18 to Apr 1 |
| Denver, CO | May 4 | Jan 12 to Feb 23 | Apr 6 to 20 |
| Colorado Springs, CO | May 3 | Jan 11 to Feb 22 | Apr 5 to 19 |
| Omaha, NE | Apr 18 | Dec 27 to Feb 7 | Mar 21 to Apr 4 |
| Aurora, CO | May 4 | Jan 12 to Feb 23 | Apr 6 to 20 |
| Lincoln, NE | Apr 24 | Jan 2 to Feb 13 | Mar 27 to Apr 10 |
| Fort Wayne, IN | Apr 24 | Jan 2 to Feb 13 | Mar 27 to Apr 10 |
| Grand Rapids, MI | Apr 29 | Jan 7 to Feb 18 | Apr 1 to 15 |
| Lakewood, CO | May 5 | Jan 13 to Feb 24 | Apr 7 to 21 |
| Springfield, MA | May 3 | Jan 11 to Feb 22 | Apr 5 to 19 |
| Joliet, IL | Apr 19 | Dec 28 to Feb 8 | Mar 22 to Apr 5 |
How to grow onionsAll zonesOnions in zone 5bOnions in zone 6bAbout zone 6a
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