When to Plant Corn in Larimer County, CO
This month in Larimer County, Colorado
May is a pivotal month for Larimer County, Colorado gardens. Focus on these tasks first and you'll set up the rest of the season for success.
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Scatter corn into prepared beds
Rake a smooth bed, make a shallow furrow, drop seeds at the spacing on the packet, water gently, walk away.
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.
Larimer County, Colorado is in USDA Zone 5b. The average last spring frost is May 2 and the first fall frost is October 6, giving you a growing season of approximately 157 days.
At an elevation of 7,108 feet, Larimer County receives approximately 23.4 inches of rainfall annually with predominantly loam soil. Summer highs average 84°F, so choose short-season varieties of Corn to ensure they mature before fall.
Larimer County Soil Profile
Soil Type
Loam
Soil pH
6.4-8.2
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 Larimer County
How your county's soil matches Corn's growing requirements.
Soil pH
Your soil pH (6.4–8.2) is more alkaline than Corn prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Larimer 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 (2.3%). Annual compost additions will help Corn.
How to Plant Corn
Succession Planting Corn
Sow every 6.9 weeks. Last sowing by Jun 28 to harvest before frost.
Plant Water Budget
Water stress score is 8/10 — 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 | — | 1.7" | 0" | ❄️ Dormant |
| Feb | — | 1.3" | 0" | ❄️ Dormant |
| Mar | — | 2.1" | 0" | ❄️ Dormant |
| Apr | — | 2.2" | 0" | ❄️ Dormant |
| May | 6.5" | 2.5" | 4" | 🚿 Regular watering |
| Jun | 6.5" | 1.9" | 4.6" | 🚿 Regular watering |
| Jul | 6.5" | 2.3" | 4.2" | 🚿 Regular watering |
| Aug | 6.5" | 2.5" | 4" | 🚿 Regular watering |
| Sep | 6.5" | 2" | 4.5" | 🚿 Regular watering |
| Oct | 6.5" | 1.9" | 4.6" | 🚿 Regular watering |
| Nov | — | 1.7" | 0" | ❄️ Dormant |
| Dec | — | 1.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Larimer 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 — Larimer County, CO
Corn Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Direct Sow | May 9 | May 9 – May 30 |
| Harvest | July 11 | Jul 11 – Sep 5 |
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 · 2-3 times/week
📅 Days to Maturity
60–100 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 5b
📆 Growing Season
157 days in Larimer County
Growing Tips for Corn in Larimer County
Direct sow Corn outdoors after May 02 in Larimer 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.
Larimer County receives only 23" 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 Larimer County, CO?
Larimer County is in Zone 5b with an average last frost of May 2. Plan your Corn planting based on this frost date — see the calendar above for exact timing.
What planting zone is Larimer County, CO?
Larimer County, Colorado is in USDA Hardiness Zone 5b. The average last spring frost is May 2 and first fall frost is October 6.
Your Larimer County Garden Planner — Free
A 24-page printable planner built for Larimer 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.