When to Plant Onion in USDA Zone 9b
Onions are a fundamental kitchen staple available in yellow, white, and red varieties. Choose long-day, short-day, or intermediate types based on your latitude.
In Zone 9b, the average last spring frost is around January 25 and the first fall frost is around December 20, giving you a growing season of approximately 329 days.
Onion Planting Timeline — Zone 9b
Where Is USDA Zone 9b?
The map below highlights the states that contain Zone 9b. Click any state to see the Onion planting schedule for that location.
Onion Planting Calendar — Zone 9b
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | December 28 | Dec 28 – Jan 11 |
| Transplant Outdoors | January 25 | Jan 25 – Feb 8 |
| Direct Sow | January 4 | Jan 4 – Jan 25 |
| Harvest | April 26 | Apr 26 – Jun 14 |
| Fall Sowing | October 25 | Oct 25 – Nov 8 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | Start Indoors Transplant Outdoors Direct Sow |
| February | Transplant Outdoors |
| March | — |
| April | Harvest |
| May | Harvest |
| June | Harvest |
| July | — |
| August | — |
| September | — |
| October | Fall Sowing |
| November | Fall Sowing |
| December | Start Indoors |
Free Zone 9b Planting Calendar PDF
Know exactly when to plant every crop in your zone. Get a printable month-by-month calendar customized for Zone 9b with start dates, transplant windows, and harvest times.
Growing Conditions
Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
Days to Maturity
90–120 days
Soil pH
6 – 7
Zone Temperature Range
25°F to 30°F average annual minimum
Growing Season
329 days (Zone 9b average)
Planting Specifications
| Planting Depth | 1 inches |
| Plant Spacing | 6 inches apart |
| Row Spacing | 12 inches between rows |
Growing Tips for Onion in Zone 9b
Zone 9b offers a long growing season (~329 days). You can plant Onion earlier and may get multiple harvests.
Start seeds indoors 8-10 weeks before transplanting. Match day-length type to your latitude. Stop watering when tops begin to fall over and cure bulbs for 2-3 weeks before storage.
Companion Planting
Good Companions
Avoid Planting Near
Level Up Your Garden
Saving Onion Seeds
Recommended for Your Garden
Reduce heat stress and sun scorch in hot climates with UV-stabilized shade cloth.
Start seeds indoors with reusable cell trays and humidity domes.
Test your soil pH, nitrogen, phosphorus, and potassium levels before planting.
Related Plants
Onion in Other Zones
Onion by State
- Alabama
- Alaska
- Arizona
- Arkansas
- California
- Colorado
- Connecticut
- Delaware
- Florida
- Georgia
- Hawaii
- Idaho
- Illinois
- Indiana
- Iowa
- Kansas
- Kentucky
- Louisiana
- Maine
- Maryland
- Massachusetts
- Michigan
- Minnesota
- Mississippi
- Missouri
- Montana
- Nebraska
- Nevada
- New Hampshire
- New Jersey
- New Mexico
- New York
- North Carolina
- North Dakota
- Ohio
- Oklahoma
- Oregon
- Pennsylvania
- Rhode Island
- South Carolina
- South Dakota
- Tennessee
- Texas
- Utah
- Vermont
- Virginia
- Washington
- West Virginia
- Wisconsin
- Wyoming
Frequently Asked Questions
When should I plant Onion in Zone 9b?
In Zone 9b, plan your Onion planting around the average last frost date of January 25. Start seeds indoors around December 28. Direct sow outdoors around January 4. Transplant seedlings around January 25.
Can Onion grow in Zone 9b?
Yes, Onion can grow well in Zone 9b, hardy in USDA zones 3a through 10b. Zone 9b has a growing season of approximately 329 days, which is sufficient for Onion (90-120 days to maturity).
When can I harvest Onion in Zone 9b?
In Zone 9b, expect to harvest Onion from April 26 – June 14. Onion takes 90-120 days from planting to harvest.
What is the last frost date for Zone 9b?
The average last spring frost in Zone 9b is around January 25, and the first fall frost is around December 20. This gives a growing season of approximately 329 days. These are 50% probability dates — actual frost dates vary year to year.
What should I plant next to Onion?
Good companion plants for Onion include Carrots, Lettuce, Beets, Cabbage. These companions can help with pest control, pollination, and nutrient sharing.
Plan Your Garden with Confidence
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