When to plant Corn in Marion County County,
Aim to plant Corn in Marion County County on or after May 8; the window stays open through May 29. Marion County County's 159-day frost-free season gives you a single solid spring crop with a brief fall option.
When to Plant Corn in Marion County, IA
Marion County, Iowa gardeners: here's your June plan
A quick June briefing for Marion County, Iowa gardeners — what's urgent, what's next, and what can wait.
July prep starts now
- 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.
Marion County, Iowa is in USDA Zone 5b. The average last spring frost is May 1 and the first fall frost is October 7, giving you a growing season of approximately 159 days.
At an elevation of 971 feet, Marion County receives approximately 33.2 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.
Marion County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-7.2
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 Marion County
How your county's soil matches Corn's growing requirements.
Soil pH
Your soil pH (6.2–7.2) overlaps with Corn's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Marion County is excellent for Corn — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (5.0%) — Corn will thrive.
How to Plant Corn
Succession Planting Corn
Sow every 6.9 weeks. Last sowing by Jun 29 to harvest before frost.
Corn 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 | — | 1.5" | 0" | ❄️ Dormant |
| Feb | — | 1.5" | 0" | ❄️ Dormant |
| Mar | — | 2.3" | 0" | ❄️ Dormant |
| Apr | — | 3.2" | 0" | ❄️ Dormant |
| May | 6.5" | 4.1" | 2.4" | 💧 Light watering |
| Jun | 6.5" | 4.1" | 2.4" | 💧 Light watering |
| Jul | 6.5" | 3.8" | 2.7" | 💧 Light watering |
| Aug | 6.5" | 3" | 3.5" | 🚿 Regular watering |
| Sep | 6.5" | 2.8" | 3.7" | 🚿 Regular watering |
| Oct | 6.5" | 2.7" | 3.8" | 🚿 Regular watering |
| Nov | — | 2.3" | 0" | ❄️ Dormant |
| Dec | — | 1.9" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Marion 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 — Marion County, IA
Corn Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | May 8 | May 8 – May 29 |
| Harvest | July 10 | Jul 10 – Sep 4 |
Plant 1" deep · 12" apart · Rows 36" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Direct Sow |
| June | — |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| 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: acceptable
🗺️ USDA Zone
Zone 5b
📆 Growing Season
159 days in Marion County
Growing Tips for Corn in Marion County
Direct sow Corn outdoors after May 01 in Marion 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 Marion County, IA?
Marion County is in Zone 5b with an average last frost of May 1. Plan your Corn planting based on this frost date — see the calendar above for exact timing.
What planting zone is Marion County, IA?
Marion County, Iowa is in USDA Hardiness Zone 5b. The average last spring frost is May 1 and first fall frost is October 7.
When should I plant Corn in Marion County County, ?
In Marion County County, , plant Corn after the last frost (around May 1) and before the first frost (around October 7). Best results when soil holds above 50°F.
What growing zone is Marion County County, for Corn?
Marion County County sits in USDA Zone 5b. Corn grows reliably in zones 3a through 11b, so it's a good fit here.
Can Corn grow in Marion County County's climate?
Yes — Corn grows well in Marion County County's temperate climate. Marion County County averages a 159-day frost-free season, with last frost around May 1 and first frost around October 7.
Your Marion County Garden Planner — Free
A 22-page printable planner built for Marion County (Zone 5b). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.