When to Plant Onion in Union County, PA
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.
Union County, Pennsylvania is in USDA Zone 6a. The average last spring frost is April 27 and the first fall frost is October 22, giving you a growing season of approximately 178 days.
At an elevation of 250 feet, Union County receives approximately 39 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Onion during the growing season.
Union County Soil Profile
Soil Type
Silt Loam
Soil pH
5.1-6.2
Drainage
Well Drained
Plant Planting Risk Windows
Percentages indicate frost risk at transplant. The 70% safe window means there is a 30% chance of frost after transplant — suitable for cold-hardy crops or gardeners with frost protection. The 90% safe window is best for tender plants.
Plant Water Budget
Onion Planting Timeline — Union County, PA
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 23 | Mar 23 – Apr 6 |
| Transplant Outdoors | April 27 | Apr 27 – May 11 |
| Direct Sow | April 13 | Apr 13 – May 4 |
| Fall Sowing | August 13 | Aug 13 – Aug 27 |
| Harvest | July 27 | Jul 27 – Sep 14 |
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 | Harvest |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Moderate — regular watering
Days to Maturity
90–120 days
Soil pH
6 – 7
USDA Zone
Zone 6a
Growing Season
178 days
Growing Tips for Union County
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
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Union County, PA?
Union County is in Zone 6a with an average last frost of April 27. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Union County, PA?
Union County, Pennsylvania is in USDA Hardiness Zone 6a. The average last spring frost is April 27 and first fall frost is October 22.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Union County gardeners in Zone 6a organize planting dates, track what's growing, and never miss a planting window.
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