When to Plant Onion in USDA Zone 5b
Your May planting checklist for Zone 5b
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Zone 5b.
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Transplant onion outside
Pinch off the lowest leaves on each seedling before you plant — it reduces water loss while the roots catch up.
Before June arrives, get these ready
- Starting indoors: onion
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 5b, the average last spring frost is around April 18 and the first fall frost is around October 13, giving you a growing season of approximately 178 days.
Onion Planting Timeline — Zone 5b
Where Is USDA Zone 5b?
The map below highlights the states that contain Zone 5b. Click any state to see the Onion planting schedule for that location.
Onion Planting Calendar — Zone 5b
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 14 | Mar 14 – Mar 28 |
| Transplant Outdoors | April 18 | Apr 18 – May 2 |
| Direct Sow | April 4 | Apr 4 – Apr 25 |
| Harvest | July 18 | Jul 18 – Sep 5 |
| Fall Sowing | August 4 | Aug 4 – Aug 18 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | Transplant Outdoors |
| June | — |
| July | Harvest |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Free Zone 5b Planting Calendar PDF
Know exactly when to plant every crop in your zone. Get a printable month-by-month calendar customized for Zone 5b 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
°F to °F average annual minimum
Growing Season
178 days (Zone average)
Planting Specifications
| Planting Depth | 1 inches |
| Plant Spacing | 6 inches apart |
| Row Spacing | 12 inches between rows |
Growing Tips for Onion in Zone
Zone has a short growing season (~178 days). Start Onion indoors early and use season-extension techniques like row covers and cold frames.
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
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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
- 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 5b?
In Zone 5b, plan your Onion planting around the average last frost date of April 18. Start seeds indoors around March 14. Direct sow outdoors around April 4. Transplant seedlings around April 18.
Can Onion grow in Zone 5b?
Yes, Onion can grow well in Zone 5b, hardy in USDA zones 3a through 10b. Zone 5b has a growing season of approximately 178 days, which is sufficient for Onion (90-120 days to maturity).
When can I harvest Onion in Zone 5b?
In Zone 5b, expect to harvest Onion from July 18 – September 5. Onion takes 90-120 days from planting to harvest.
What is the last frost date for Zone 5b?
The average last spring frost in Zone 5b is around April 18, and the first fall frost is around October 13. This gives a growing season of approximately 178 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.
Your Free Printable Garden Planner
A 24-page printable planner tailored to your zone. Planting dates, monthly task lists, harvest log, seed inventory, and succession charts — everything you need to plan a full season.