When to plant onions in zone 9b
In zone 9b, where the last spring frost typically comes around January 31, start onions indoors October 11 to November 22 and plant out January 3 to 17.
The zone 9b schedule for onions
- Start seeds indoors
- October 11 to November 22
- Plant out
- January 3 to 17
- Sow outdoors
- December 20 to January 3
From the median frost dates of the NOAA stations assigned to the 1,459 ZIP codes in zone 9b, 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 9b
Zones are based on winter cold, not on frost dates, so the last spring frost varies a lot within a zone. Across zone 9b, the typical last frost ranges from about January 12 in the earliest tenth of ZIP codes to March 1 in the latest tenth, and the first fall frost from January 8 to December 28. For a typical place in the zone:
- December 18Risky: a later frost happens in 9 years out of 10
- January 31Typical: frost after this date in half of years
- March 1Safe: 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 9b cities
| City | Typical last frost | Start indoors | Plant out |
|---|---|---|---|
| Houston, TX | Jan 30 | Oct 10 to Nov 21 | Jan 2 to 16 |
| Jacksonville, FL | Feb 1 | Oct 12 to Nov 23 | Jan 4 to 18 |
| San Jose, CA | Jan 12 | Sep 22 to Nov 3 | Dec 15 to 29 |
| Fresno, CA | Jan 14 | Sep 24 to Nov 5 | Dec 17 to 31 |
| Sacramento, CA | Jan 12 | Sep 22 to Nov 3 | Dec 15 to 29 |
| Bakersfield, CA | Jan 17 | Sep 27 to Nov 8 | Dec 20 to Jan 3 |
| New Orleans, LA | Jan 24 | Oct 4 to Nov 15 | Dec 27 to Jan 10 |
| Henderson, NV | Jan 20 | Sep 30 to Nov 11 | Dec 23 to Jan 6 |
How to grow onionsAll zonesOnions in zone 9aAbout zone 9b
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