When to Plant Onion in Kootenai County, ID
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.
Kootenai County, Idaho is in USDA Zone 6a. The average last spring frost is April 29 and the first fall frost is October 8, giving you a growing season of approximately 162 days.
At an elevation of 5,986 feet, Kootenai County receives approximately 20.7 inches of rainfall annually with predominantly loam soil. Summer highs average 86°F, providing good warmth for Onion during the growing season.
Kootenai County Soil Profile
Soil Type
Loam
Soil pH
6.7-7.7
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 — Kootenai County, ID
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 25 | Mar 25 – Apr 8 |
| Transplant Outdoors | April 29 | Apr 29 – May 13 |
| Direct Sow | April 15 | Apr 15 – May 6 |
| Fall Sowing | July 30 | Jul 30 – Aug 13 |
| Harvest | July 29 | Jul 29 – Sep 16 |
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 | — |
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
162 days
Growing Tips for Kootenai 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 Kootenai County, ID?
Kootenai County is in Zone 6a with an average last frost of April 29. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Kootenai County, ID?
Kootenai County, Idaho is in USDA Hardiness Zone 6a. The average last spring frost is April 29 and first fall frost is October 8.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Kootenai County gardeners in Zone 6a organize planting dates, track what's growing, and never miss a planting window.
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