When to Plant Onion in USDA Zone 5a
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 5a, the average last spring frost is around April 25 and the first fall frost is around October 8, giving you a growing season of approximately 166 days.
Onion Planting Timeline — Zone 5a
Where Is USDA Zone 5a?
The map below highlights the states that contain Zone 5a. Click any state to see the Onion planting schedule for that location.
Onion Planting Calendar — Zone 5a
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 21 | Mar 21 – Apr 4 |
| Transplant Outdoors | April 25 | Apr 25 – May 9 |
| Direct Sow | April 11 | Apr 11 – May 2 |
| Fall Sowing | July 30 | Jul 30 – Aug 13 |
| Harvest | July 25 | Jul 25 – Sep 12 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | — |
| July | Fall Sowing Harvest |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Free Zone 5a Planting Calendar PDF
Know exactly when to plant every crop in your zone. Get a printable month-by-month calendar customized for Zone 5a 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
-20°F to -15°F average annual minimum
Growing Season
166 days (Zone 5a average)
Planting Specifications
| Planting Depth | 1 inches |
| Plant Spacing | 6 inches apart |
| Row Spacing | 12 inches between rows |
Growing Tips for Zone 5a
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
Start seeds indoors with reusable cell trays and humidity domes.
Test your soil pH, nitrogen, phosphorus, and potassium levels before planting.
Keep your garden organized with durable, weather-resistant plant labels.
Related Plants
Onion in Other Zones
Onion by State
- Alabama
- Alaska
- Alberta
- Arizona
- Arkansas
- British Columbia
- California
- Colorado
- Connecticut
- Delaware
- Florida
- Georgia
- Hawaii
- Idaho
- Illinois
- Indiana
- Iowa
- Kansas
- Kentucky
- Louisiana
- Maine
- Manitoba
- Maryland
- Massachusetts
- Michigan
- Minnesota
- Mississippi
- Missouri
- Montana
- Nebraska
- Nevada
- New Brunswick
- New Hampshire
- New Jersey
- New Mexico
- New York
- Newfoundland and Labrador
- North Carolina
- North Dakota
- Northwest Territories
- Nova Scotia
- Nunavut
- Ohio
- Oklahoma
- Ontario
- Oregon
- Pennsylvania
- Prince Edward Island
- Quebec
- Rhode Island
- Saskatchewan
- South Carolina
- South Dakota
- Tennessee
- Texas
- Utah
- Vermont
- Virginia
- Washington
- West Virginia
- Wisconsin
- Wyoming
- Yukon
Frequently Asked Questions
When should I plant Onion in Zone 5a?
In Zone 5a, plan your Onion planting around the average last frost date of April 25. Start seeds indoors around March 21. Direct sow outdoors around April 11. Transplant seedlings around April 25.
Can Onion grow in Zone 5a?
Yes, Onion can grow well in Zone 5a, hardy in USDA zones 3a through 10b. Zone 5a has a growing season of approximately 166 days, which is sufficient for Onion (90-120 days to maturity).
When can I harvest Onion in Zone 5a?
In Zone 5a, expect to harvest Onion from July 25 – September 12. Onion takes 90-120 days from planting to harvest.
What is the last frost date for Zone 5a?
The average last spring frost in Zone 5a is around April 25, and the first fall frost is around October 8. This gives a growing season of approximately 166 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
Get our free Garden Planner — organize your planting dates for Zone 5a, track your crops, and plan your garden season from seed to harvest.
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