When to Plant Corn in McHenry County, IL
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.
McHenry County, Illinois is in USDA Zone 5a. The average last spring frost is April 18 and the first fall frost is October 20, giving you a growing season of approximately 185 days.
At an elevation of 640 feet, McHenry County receives approximately 39.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Corn to ensure they mature before fall.
McHenry County Soil Profile
Soil Type
Silt Loam
Soil pH
5.9-6.7
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.
Soil Compatibility in McHenry County
How your county's soil matches Corn's growing requirements.
Soil pH
Your soil pH (5.9–6.7) overlaps with Corn's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in McHenry County is excellent for Corn — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.1%) — Corn will thrive.
How to Plant Corn
Succession Planting Corn
Sow every 6.9 weeks. Last sowing by Jul 12 to harvest before frost.
Plant 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 | — | 1.6" | 0" | ❄️ Dormant |
| Feb | — | 1.9" | 0" | ❄️ Dormant |
| Mar | — | 2.5" | 0" | ❄️ Dormant |
| Apr | 6.5" | 4.2" | 2.3" | 💧 Light watering |
| May | 6.5" | 4.2" | 2.3" | 💧 Light watering |
| Jun | 6.5" | 4.8" | 1.7" | 💧 Light watering |
| Jul | 6.5" | 4.1" | 2.4" | 💧 Light watering |
| Aug | 6.5" | 4.5" | 2" | 💧 Light watering |
| Sep | 6.5" | 3.3" | 3.2" | 💧 Light watering |
| Oct | 6.5" | 3.4" | 3.1" | 💧 Light watering |
| Nov | — | 2.7" | 0" | ❄️ Dormant |
| Dec | — | 2.2" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in McHenry 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 — McHenry County, IL
Corn Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | April 25 | Apr 25 – May 16 |
| Harvest | June 27 | Jun 27 – Aug 22 |
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 · 2-3 times/week
📅 Days to Maturity
60–100 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 5a
📆 Growing Season
185 days in McHenry County
Growing Tips for Corn in McHenry County
Direct sow Corn outdoors after April 18 in McHenry 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 McHenry County, IL?
McHenry County is in Zone 5a with an average last frost of April 18. Plan your Corn planting based on this frost date — see the calendar above for exact timing.
What planting zone is McHenry County, IL?
McHenry County, Illinois is in USDA Hardiness Zone 5a. The average last spring frost is April 18 and first fall frost is October 20.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help McHenry County gardeners in Zone 5a organize planting dates, track what's growing, and never miss a planting window.
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