When to Plant Butternut Squash in Iron County, WI
Your May game plan for Iron County, Wisconsin
We've pulled the most time-sensitive tasks for Iron County, Wisconsin this May and put them front and centre. Tackle them in order.
Get ahead of June
- Transplants going out: butternut squash
- Direct-sowing: butternut squash
Butternut squash is a popular winter squash with a long neck, small seed cavity, and sweet, nutty orange flesh. It stores exceptionally well for months.
Iron County, Wisconsin is in USDA Zone 4a. The average last spring frost is May 22 and the first fall frost is September 25, giving you a growing season of approximately 126 days.
At an elevation of 841 feet, Iron County receives approximately 32.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 78°F, so choose short-season varieties of Butternut Squash to ensure they mature before fall.
Iron County Soil Profile
Soil Type
Silt Loam
Soil pH
5.7-6.9
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 Iron County
How your county's soil matches Butternut Squash's growing requirements.
Soil pH
Your soil pH (5.7–6.9) overlaps with Butternut Squash's range (6.0–7.0), though not a perfect match.
Soil Texture
The silt loam soil in Iron County is excellent for Butternut Squash — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.6%) — Butternut Squash will thrive.
How to Plant Butternut Squash
Plant Water Budget
Monthly Watering Guide for Butternut Squash
Butternut Squash needs approximately 1.1 inches of water per week (4.8" per month). Here's how your county's rainfall compares month by month.
| Month | Butternut Squash Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.2" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.4" | 0" | ❄️ Dormant |
| Apr | — | 3" | 0" | ❄️ Dormant |
| May | 4.8" | 3.7" | 1.1" | 💧 Light watering |
| Jun | 4.8" | 3.6" | 1.2" | 💧 Light watering |
| Jul | 4.8" | 3.6" | 1.2" | 💧 Light watering |
| Aug | 4.8" | 3.7" | 1.1" | 💧 Light watering |
| Sep | 4.8" | 3.2" | 1.6" | 💧 Light watering |
| Oct | — | 2.5" | 0" | ❄️ Dormant |
| Nov | — | 2.3" | 0" | ❄️ Dormant |
| Dec | — | 1.8" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Iron County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Butternut Squash 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.
Butternut Squash Planting Timeline — Iron County, WI
Butternut Squash Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | April 10 | Apr 10 – Apr 24 |
| Transplant Outdoors | June 12 | Jun 12 – Jun 26 |
| Direct Sow | June 5 | Jun 5 – Jun 26 |
| Harvest | September 11 | Sep 11 – Oct 16 |
Plant 1" deep · 30" apart · Rows 42" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Start Indoors |
| May | — |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | — |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1.1"/week · Only during dry spells
📅 Days to Maturity
85–110 days
🧪 Soil pH
Needs 6–7 · Your soil: acceptable
🗺️ USDA Zone
Zone 4a
📆 Growing Season
126 days in Iron County
Growing Tips for Butternut Squash in Iron County
Direct sow Butternut Squash outdoors after May 22 in Iron County when soil has warmed and frost danger has passed.
Common pests for Butternut Squash in this region include squash vine borer and cucumber beetles. Use row covers early in the season and inspect plants weekly.
General growing tips
Start seeds indoors 3 weeks early or direct sow after frost. Allow 6-8 feet for sprawling vines. Harvest when the skin is hard and uniformly tan. Cure in the sun for 10 days.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Butternut Squash in Other Locations
Frequently Asked Questions
When should I plant Butternut Squash in Iron County, WI?
Iron County is in Zone 4a with an average last frost of May 22. Plan your Butternut Squash planting based on this frost date — see the calendar above for exact timing.
What planting zone is Iron County, WI?
Iron County, Wisconsin is in USDA Hardiness Zone 4a. The average last spring frost is May 22 and first fall frost is September 25.
Your Iron County Garden Planner — Free
A 24-page printable planner built for Iron County (Zone 4a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.