When to Plant Corn in Caribou County, ID
Corn is a warm-season grass grown for its sweet ears, which are best eaten soon after harvest. It is wind-pollinated and must be planted in blocks for good kernel fill.
Caribou County, Idaho is in USDA Zone 4b. The average last spring frost is May 30 and the first fall frost is September 16, giving you a growing season of approximately 109 days.
At an elevation of 6,562 feet, Caribou County receives approximately 15.3 inches of rainfall annually with predominantly loam soil. Summer highs average 81°F, so choose short-season varieties of Corn to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Corn successfully. Mulch heavily to conserve soil moisture.
Caribou County Soil Profile
Soil Type
Loam
Soil pH
6.8-8.1
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 Caribou County
How your county's soil matches Corn's growing requirements.
Soil pH
Your soil pH (6.8–8.1) is more alkaline than Corn prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Caribou County is excellent for Corn — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.7%). Annual compost additions will help Corn.
How to Plant Corn
Succession Planting Corn
Sow every 6.9 weeks. Last sowing by Jun 08 to harvest before frost.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Corn
Corn needs approximately 1.5 inches of water per week (6.5" per month). Here's how your county's rainfall compares month by month.
| Month | Corn Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.2" | 0" | ❄️ Dormant |
| Feb | — | 0.9" | 0" | ❄️ Dormant |
| Mar | — | 1.4" | 0" | ❄️ Dormant |
| Apr | — | 1.7" | 0" | ❄️ Dormant |
| May | 6.5" | 1.6" | 4.9" | 🚿 Regular watering |
| Jun | 6.5" | 1" | 5.5" | 🚿 Regular watering |
| Jul | 6.5" | 1.5" | 5" | 🚿 Regular watering |
| Aug | 6.5" | 1.4" | 5.1" | 🚿 Regular watering |
| Sep | 6.5" | 1.2" | 5.3" | 🚿 Regular watering |
| Oct | — | 1.4" | 0" | ❄️ Dormant |
| Nov | — | 1.1" | 0" | ❄️ Dormant |
| Dec | — | 0.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Caribou County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Corn 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.
Corn Planting Timeline — Caribou County, ID
Corn Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | June 13 | Jun 13 – Jul 4 |
| Harvest | August 15 | Aug 15 – Oct 10 |
Plant 1" deep · 12" apart · Rows 36" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | — |
| June | Direct Sow |
| July | Direct Sow |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.5"/week · 2-3 times/week
📅 Days to Maturity
60–100 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 4b
📆 Growing Season
109 days in Caribou County
Growing Tips for Corn in Caribou County
Direct sow Corn outdoors after May 30 in Caribou County when soil has warmed and frost danger has passed.
Your 109.0-day growing season in Caribou County is tight for Corn (60.0-100.0 days to maturity). Start indoors and choose early-maturing varieties.
Common pests for Corn in this region include corn earworm and corn borers. Use row covers early in the season and inspect plants weekly.
Caribou County receives only 15" of rain annually. Corn needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Plant in blocks of at least 4 rows rather than single rows for proper pollination. Direct sow after soil reaches 60F. Side-dress with nitrogen when plants are knee-high.
Recommended Corn Varieties for Caribou County
Ultra-early corn varieties for your season
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Corn in Other Locations
Frequently Asked Questions
When should I plant Corn in Caribou County, ID?
Caribou County is in Zone 4b with an average last frost of May 30. Plan your Corn planting based on this frost date — see the calendar above for exact timing.
What planting zone is Caribou County, ID?
Caribou County, Idaho is in USDA Hardiness Zone 4b. The average last spring frost is May 30 and first fall frost is September 16.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Caribou County gardeners in Zone 4b organize planting dates, track what's growing, and never miss a planting window.
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