When to plant onions
Onions tolerate frost, so start seeds indoors 10–12 weeks before your last frost; transplant 2–4 weeks before it. Plant when the soil is at least 45°F.
Onions dates for Columbus, Ohio (example)
Example dates. Enter your ZIP above for your own.
| Start indoors | Jan 26 – Feb 9 |
|---|---|
| Transplant outside | Mar 23 – Apr 6 |
| Last planting for a harvest before frost | Jul 10 |
| Soil temperature | 45°F or warmer |
| Days to harvest | 90–120 |
| Spacing | 4–6 in apart |
Your onion year
- Start indoors
- Transplant outside
Average last frost Apr 20, first frost Oct 24.
Growing tips for onions
- Choose by latitude: long-day onions north of about 37°N, short-day onions in the South.
- Onion sets and transplants tolerate light frost, so they go in a month before the last frost.
- Bulbs are ready when about half the tops have flopped over.
Work out indoor sowing for everything at once with the seed starting calculator.
When to plant onions in major cities
Calculated from each city's NOAA 1991–2020 average frost dates.
| City | Zone | Transplant |
|---|---|---|
| New York, NY | 7b | Mar 2–16 |
| Chicago, IL | 6b | Mar 13–27 |
| Los Angeles, CA | 10b | Dec 28 – Jan 11 |
| Houston, TX | 9b | Jan 5–19 |
| Phoenix, AZ | 10a | Dec 8–22 |
| Philadelphia, PA | 7b | Mar 2–16 |
| Dallas, TX | 8b | Feb 2–16 |
| Atlanta, GA | 8a | Feb 24 – Mar 10 |
| Seattle, WA | 9a | Feb 13–27 |
| Denver, CO | 6a | Apr 2–16 |
| Boston, MA | 7a | Mar 7–21 |
| Minneapolis, MN | 5a | Mar 26 – Apr 9 |
| Kansas City, MO | 6b | Mar 7–21 |
| Nashville, TN | 7b | Mar 4–18 |
| Portland, OR | 9a | Jan 28 – Feb 11 |
| Salt Lake City, UT | 7b | Mar 3–17 |
| Columbus, OH | 6b | Mar 23 – Apr 6 |
| Charlotte, NC | 8a | Mar 2–16 |
| Detroit, MI | 6b | Mar 24 – Apr 7 |
| Raleigh, NC | 8a | Feb 28 – Mar 14 |
Onions planting FAQ
When should I plant onions?
Onions tolerate frost, so start seeds indoors 10–12 weeks before your last frost; transplant 2–4 weeks before it. Plant when the soil is at least 45°F.
How many days until onions are ready to harvest?
Most onion varieties take about 90–120 days from transplanting. Check the seed packet: early varieties are at the low end.
Can onions survive frost?
Yes. Onions tolerate frost and light freezes, which is why they can be planted weeks before the last frost date.
How far apart should I plant onions?
Space onions 4–6 in apart.
What is the last date I can plant onions?
Count the variety's days to maturity back from your first fall frost, allowing a week or two extra because onions tolerate light frost. Enter your ZIP code on this page and Seasonwise calculates the date for you.
Ask about growing onions
Enter your ZIP above first and answers will use your local frost dates. Written by an AI model; double-check anything important.