When to plant onions
Short answer
Onions are hardy: seeds or sets can go in 2–4 weeks before your average last frost. Seeds need soil of at least 35 °F to sprout.[1, 2]
Onions at a glance
| Frost tolerance | Hardy [1, 2] |
|---|---|
| Plant outside (seeds or sets) | 2–4 weeks before the average last frost [1, 2] |
| Soil temperature for seeds | At least 35 °F; best around 80 °F [1] |
| Time to harvest | About 110 days for dry bulbs; about 60 for green onions [1] |
Spring and fall planting
- Spring, seeds or sets: Can go in as early as 2–4 weeks before the average last frost, once the soil has dried out. [1, 2]
- Spring, transplants: Set out onion transplants in early spring. [3]
- Fall, sets: In South Carolina, onion sets are also planted in fall. [3]
Example dates for some US cities
Based on each city's main airport weather station: the date with an even chance of frost after it (32 °F). [4] Your own dates can differ: use the ZIP code box above.
| City | Average last frost | Plant outside |
|---|---|---|
| New York, NY | Mar 30 | Mar 2 – Mar 16 |
| Atlanta, GA | Mar 15 | Feb 15 – Mar 1 |
| Dallas–Fort Worth, TX | Mar 8 | Feb 8 – Feb 22 |
| Chicago, IL | Apr 16 | Mar 19 – Apr 2 |
| Denver, CO | May 5 | Apr 7 – Apr 21 |
| Minneapolis, MN | Apr 23 | Mar 26 – Apr 9 |
| Seattle, WA | Mar 2 | Feb 2 – Feb 16 |
Questions people ask
Can onions survive frost?
Hardy crops like onions grow in daytime temperatures as low as 40 °F and may survive a frosty night. [1]
What soil temperature do onions seeds need?
At least 35 °F; they sprout best around 80 °F. [1]
How long do onions take to grow?
About 110 days for dry bulbs; about 60 for green onions. [1]
Sources
Facts on this page were checked against these sources on November 6, 2026. The wording is our own. Frost dates: NOAA NCEI, U.S. Climate Normals 1991–2020; NOAA does not endorse this site. Some guides are written for Utah or South Carolina: we use only their general rules, not their local calendar dates.
- Vegetable Planting Guide (CMG GardenNotes #720). Colorado State University Extension. Reviewed Sep 2024.
- Suggested Vegetable Planting Dates for Utah. Utah State University Extension. Revised May 2025.
- Onion, Leek, Shallot, & Garlic (HGIC 1314). Clemson Cooperative Extension. Updated Jan 20, 2023.
- U.S. Climate Normals 1991–2020 (frost dates). NOAA National Centers for Environmental Information.
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