When to plant Corn in Washington County County,
Washington County County sits in cold Zone 7a. Plant Corn May 16–June 6 for the single annual harvest; the October 1 first frost closes the window.
When to Plant Corn in Washington County, ID
Top priorities for Washington County, Idaho gardeners in June
Your Washington County, Idaho garden is entering a new phase. Here's what's on the schedule for June and why each task matters now.
Before July arrives, get these ready
- First harvests: corn
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.
Washington County, Idaho is in USDA Zone 7a. The average last spring frost is May 9 and the first fall frost is October 1, giving you a growing season of approximately 145 days.
At an elevation of 4,048 feet, Washington County receives approximately 17.9 inches of rainfall annually with predominantly loam soil. Summer highs average 85°F, providing good warmth for Corn during the growing season. With low rainfall, drip irrigation is essential for growing Corn successfully. Mulch heavily to conserve soil moisture.
Washington County Soil Profile
Soil Type
Loam
Soil pH
6.2-7.8
Drainage
Well Drained
Corn 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 Washington County
How your county's soil matches Corn's growing requirements.
Soil pH
Your soil pH (6.2–7.8) overlaps with Corn's range (6.0–7.0), though not a perfect match.
Soil Texture
The loam soil in Washington County is excellent for Corn — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Corn.
Organic Matter
Organic matter is moderate (2.5%). Annual compost additions will help Corn.
How to Plant Corn
Succession Planting Corn
Sow every 6.9 weeks. Last sowing by Jun 23 to harvest before frost.
Corn Water Budget
Water stress score is 6/10 — 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 | — | 1.1" | 0" | ❄️ Dormant |
| Feb | — | 1.2" | 0" | ❄️ Dormant |
| Mar | — | 1.9" | 0" | ❄️ Dormant |
| Apr | — | 1.7" | 0" | ❄️ Dormant |
| May | 6.5" | 2" | 4.5" | 🚿 Regular watering |
| Jun | 6.5" | 1.2" | 5.3" | 🚿 Regular watering |
| Jul | 6.5" | 1.6" | 4.9" | 🚿 Regular watering |
| Aug | 6.5" | 1.7" | 4.8" | 🚿 Regular watering |
| Sep | 6.5" | 1.5" | 5" | 🚿 Regular watering |
| Oct | 6.5" | 1.5" | 5" | 🚿 Regular watering |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Washington 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 — Washington County, ID
Corn Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | May 16 | May 16 – Jun 6 |
| Harvest | July 18 | Jul 18 – Sep 12 |
Plant 1" deep · 12" apart · Rows 36" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Direct Sow |
| June | Direct Sow |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| 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: acceptable
🗺️ USDA Zone
Zone 7a
📆 Growing Season
145 days in Washington County
Growing Tips for Corn in Washington County
Direct sow Corn outdoors after May 09 in Washington County when soil has warmed and frost danger has passed.
Common pests for Corn in this region include corn earworm and corn borers. Use row covers early in the season and inspect plants weekly.
Washington County receives only 18" 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.
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 Washington County, ID?
Washington County is in Zone 7a with an average last frost of May 9. Plan your Corn planting based on this frost date — see the calendar above for exact timing.
What planting zone is Washington County, ID?
Washington County, Idaho is in USDA Hardiness Zone 7a. The average last spring frost is May 9 and first fall frost is October 1.
When should I plant Corn in Washington County, ?
In Washington County, , plant Corn after the last frost (around May 9) and before the first frost (around October 1). Best results when soil holds above 50°F.
What growing zone is Washington County, for Corn?
Washington County sits in USDA Zone 7a. Corn grows reliably in zones 3a through 11b, so it's a good fit here.
Can Corn grow in Washington County's climate?
Yes — Corn grows well in Washington County's temperate climate. Washington County averages a 145-day frost-free season, with last frost around May 9 and first frost around October 1.
Your Washington County Garden Planner — Free
A 22-page printable planner built for Washington County (Zone 7a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.