When to plant Sweet Corn in Marshall County, IA
Aim to plant Sweet Corn in Marshall County on or after May 9; the window stays open through May 30. Marshall County's 158-day frost-free season gives you a single solid spring crop with a brief fall option.
When to Plant Sweet Corn in Marshall County, IA
Sweet corn is bred for high sugar content in its kernels, which convert to starch rapidly after harvest. Modern supersweet varieties hold their sweetness longer.
Marshall County, Iowa is in USDA Zone 5a. The average last spring frost is May 2 and the first fall frost is October 7, giving you a growing season of approximately 158 days.
At an elevation of 1,379 feet, Marshall County receives approximately 33.1 inches of rainfall annually with predominantly silt loam soil. Summer highs average 83°F, so choose short-season varieties of Sweet Corn to ensure they mature before fall.
Marshall County Soil Profile
Soil Type
Silt Loam
Soil pH
6.0-7.0
Drainage
Well Drained
Sweet Corn Planting Timeline — Marshall County, IA
Sweet Corn Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | May 9 | May 9 – May 30 |
| Harvest | July 11 | Jul 11 – Aug 22 |
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 | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
Moderate — regular watering
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–7 · Your soil: N/A
🗺️ USDA Zone
Zone 5a
📆 Growing Season
158 days in Marshall County
Growing Tips for Marshall County
Plant in blocks of at least 4 rows for wind pollination. Direct sow after soil is warm. Isolate supersweet varieties from other corn types to prevent cross-pollination.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Sweet Corn in Other Locations
Frequently Asked Questions
When should I plant Sweet Corn in Marshall County, IA?
Marshall County is in Zone 5a with an average last frost of May 2. Plan your Sweet Corn planting based on this frost date — see the calendar above for exact timing.
What planting zone is Marshall County, IA?
Marshall County, Iowa is in USDA Hardiness Zone 5a. The average last spring frost is May 2 and first fall frost is October 7.
When should I plant Sweet Corn in Marshall County, IA?
In Marshall County, IA, plant Sweet Corn after the last frost (around May 2) and before the first frost (around October 7). Best results when soil holds above 50°F.
What growing zone is Marshall County, IA for Sweet Corn?
Marshall County sits in USDA Zone 5a. Sweet Corn grows reliably in zones 3a through 11b, so it's a good fit here.
Can Sweet Corn grow in Marshall County's climate?
Yes — Sweet Corn grows well in Marshall County's temperate climate. Marshall County averages a 158-day frost-free season, with last frost around May 2 and first frost around October 7.
Your Marshall County Garden Planner — Free
A 22-page printable planner built for Marshall County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.