When to Plant Corn in Whatcom County, WA
May in the garden — Whatcom County, Washington
We've pulled the most time-sensitive tasks for Whatcom County, Washington this May and put them front and centre. Tackle them in order.
Looking ahead to June
- 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.
Whatcom County, Washington is in USDA Zone 8a. The average last spring frost is April 6 and the first fall frost is October 29, giving you a growing season of approximately 206 days.
At an elevation of 386 feet, Whatcom County receives approximately 49 inches of rainfall annually with predominantly silt loam soil. Summer highs average 85°F, providing good warmth for Corn during the growing season.
Whatcom County Soil Profile
Soil Type
Silt Loam
Soil pH
5.2-6.4
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 Whatcom County
How your county's soil matches Corn's growing requirements.
Soil pH
Your soil pH (5.2–6.4) is more acidic than Corn prefers (6.0–7.0). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Whatcom County is excellent for Corn — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.7%) — Corn will thrive.
How to Plant Corn
Succession Planting Corn
Sow every 6.9 weeks. Last sowing by Jul 21 to harvest before frost.
Plant Water Budget
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 | — | 6.1" | 0" | ❄️ Dormant |
| Feb | — | 6.2" | 0" | ❄️ Dormant |
| Mar | — | 4.3" | 0" | ❄️ Dormant |
| Apr | 6.5" | 3.8" | 2.7" | 💧 Light watering |
| May | 6.5" | 3.1" | 3.4" | 🚿 Regular watering |
| Jun | 6.5" | 2.1" | 4.4" | 🚿 Regular watering |
| Jul | 6.5" | 0.7" | 5.8" | 🚿 Regular watering |
| Aug | 6.5" | 0.9" | 5.6" | 🚿 Regular watering |
| Sep | 6.5" | 2" | 4.5" | 🚿 Regular watering |
| Oct | 6.5" | 4.5" | 2" | 💧 Light watering |
| Nov | — | 7.1" | 0" | ❄️ Dormant |
| Dec | — | 8.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Whatcom 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 — Whatcom County, WA
Corn Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | April 13 | Apr 13 – May 4 |
| Harvest | June 15 | Jun 15 – Aug 10 |
Plant 1" deep · 12" apart · Rows 36" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Direct Sow |
| May | Direct Sow |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.5"/week · 1-2 times/week
📅 Days to Maturity
60–100 days
🧪 Soil pH
Needs 6–7 · Your soil: too_acidic
🗺️ USDA Zone
Zone 8a
📆 Growing Season
206 days in Whatcom County
Growing Tips for Corn in Whatcom County
Direct sow Corn outdoors after April 06 in Whatcom 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.
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 Whatcom County, WA?
Whatcom County is in Zone 8a with an average last frost of April 6. Plan your Corn planting based on this frost date — see the calendar above for exact timing.
What planting zone is Whatcom County, WA?
Whatcom County, Washington is in USDA Hardiness Zone 8a. The average last spring frost is April 6 and first fall frost is October 29.
Your Whatcom County Garden Planner — Free
A 24-page printable planner built for Whatcom County (Zone 8a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.