When to Plant Onion in Sanpete County, UT
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.
Sanpete County, Utah is in USDA Zone 5b. The average last spring frost is May 21 and the first fall frost is September 28, giving you a growing season of approximately 130 days.
At an elevation of 6,969 feet, Sanpete County receives approximately 14.2 inches of rainfall annually with predominantly loam soil. Summer highs average 86°F, providing good warmth for Onion during the growing season. With low rainfall, drip irrigation is essential for growing Onion successfully. Mulch heavily to conserve soil moisture.
Sanpete County Soil Profile
Soil Type
Loam
Soil pH
6.5-7.8
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
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Onion Planting Timeline — Sanpete County, UT
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 16 | Apr 16 – Apr 30 |
| Transplant Outdoors | May 21 | May 21 – Jun 4 |
| Direct Sow | May 7 | May 7 – May 28 |
| Fall Sowing | July 20 | Jul 20 – Aug 3 |
| Harvest | August 20 | Aug 20 – Oct 8 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Transplant Outdoors Direct Sow |
| June | Transplant Outdoors |
| July | Fall Sowing |
| August | Fall Sowing Harvest |
| September | Harvest |
| October | Harvest |
| 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 5b
Growing Season
130 days
Growing Tips for Sanpete 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 Sanpete County, UT?
Sanpete County is in Zone 5b with an average last frost of May 21. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Sanpete County, UT?
Sanpete County, Utah is in USDA Hardiness Zone 5b. The average last spring frost is May 21 and first fall frost is September 28.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Sanpete County gardeners in Zone 5b organize planting dates, track what's growing, and never miss a planting window.
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