When to Plant Onion in Bannock County, ID
May in Bannock County, Idaho — your action list
Your garden in Bannock County, Idaho is working on a schedule, even when you're not. Here's where you should be this May.
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Harden off and plant onion
Pinch off the lowest leaves on each seedling before you plant — it reduces water loss while the roots catch up.
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Seed onion outdoors
Your soil is 42°F — warm enough for these to germinate without babying.
Get ahead of June
- 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.
Bannock County, Idaho is in USDA Zone 6a. The average last spring frost is May 23 and the first fall frost is September 24, giving you a growing season of approximately 124 days.
At an elevation of 5,637 feet, Bannock County receives approximately 13.1 inches of rainfall annually with predominantly loam soil. Summer highs average 83°F, so choose short-season varieties of Onion to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Onion successfully. Mulch heavily to conserve soil moisture.
Bannock County Soil Profile
Soil Type
Loam
Soil pH
6.7-8.1
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.
Soil Compatibility in Bannock County
How your county's soil matches Onion's growing requirements.
Soil pH
Your soil pH (6.7–8.1) is more alkaline than Onion prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Bannock County is excellent for Onion — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.4%). Annual compost additions will help Onion.
How to Plant Onion
Fall planting: Sow 10 weeks before your first frost date for a fall harvest.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Onion
Onion needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.
| Month | Onion Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1" | 0" | ❄️ Dormant |
| Feb | — | 0.8" | 0" | ❄️ Dormant |
| Mar | — | 1.1" | 0" | ❄️ Dormant |
| Apr | — | 1.4" | 0" | ❄️ Dormant |
| May | 4.3" | 1.5" | 2.8" | 🚿 Regular watering |
| Jun | 4.3" | 0.9" | 3.4" | 🚿 Regular watering |
| Jul | 4.3" | 1.1" | 3.2" | 🚿 Regular watering |
| Aug | 4.3" | 1.4" | 2.9" | 🚿 Regular watering |
| Sep | 4.3" | 1" | 3.3" | 🚿 Regular watering |
| Oct | — | 1" | 0" | ❄️ Dormant |
| Nov | — | 1" | 0" | ❄️ Dormant |
| Dec | — | 0.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Bannock County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Onion Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Onion Planting Timeline — Bannock County, ID
Onion Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 18 | Apr 18 – May 2 |
| Transplant Outdoors | May 23 | May 23 – Jun 6 |
| Direct Sow | May 9 | May 9 – May 30 |
| Harvest | August 22 | Aug 22 – Oct 10 |
| Fall Sowing | July 16 | Jul 16 – Jul 30 |
Plant 1" deep · 6" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | Start Indoors Transplant Outdoors Direct Sow |
| June | Transplant Outdoors |
| July | Fall Sowing |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · 1-2 times/week
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 6a
📆 Growing Season
124 days in Bannock County
Growing Tips for Onion in Bannock County
Direct sow Onion outdoors after May 23 in Bannock County when soil has warmed and frost danger has passed.
Your 124.0-day growing season in Bannock County is tight for Onion (90.0-120.0 days to maturity). Start indoors and choose early-maturing varieties.
Common pests for Onion in this region include onion maggots and thrips. Use row covers early in the season and inspect plants weekly.
Bannock County receives only 13" of rain annually. Onion needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
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
Check more plant combinations with our Companion Planting Checker →
Onion in Other Locations
Frequently Asked Questions
When should I plant Onion in Bannock County, ID?
Bannock County is in Zone 6a with an average last frost of May 23. Plan your Onion planting based on this frost date — see the calendar above for exact timing.
What planting zone is Bannock County, ID?
Bannock County, Idaho is in USDA Hardiness Zone 6a. The average last spring frost is May 23 and first fall frost is September 24.
Your Bannock County Garden Planner — Free
A 24-page printable planner built for Bannock County (Zone 6a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.