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When to Plant Squash (Summer) in Washburn County, WI

Washburn County, Wisconsin Zone 4a May

Your May game plan for Washburn County, Wisconsin

Welcome to May in Zone 4a. These are the moves that will have the biggest impact on your growing season.

Avg. last frost May 17
Avg. first frost September 25
Soil temp (4") 50°F
Watering Moderate
Pest pressure Low
Daylight 14.7 hrs
  1. Put squash (summer) seeds straight in the ground

    Thin ruthlessly once seedlings are up. Crowded roots mean smaller crops from every plant.

A few tasks this May that'll pay off in June
  • Transplants going out: squash (summer)
  • Starting indoors: squash (summer)

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Summer squash includes zucchini, yellow crookneck, and pattypan varieties that are harvested young and tender. They are prolific producers in warm weather.

Washburn County, Wisconsin is in USDA Zone 4a. The average last spring frost is May 17 and the first fall frost is September 25, giving you a growing season of approximately 131 days.

At an elevation of 954 feet, Washburn County receives approximately 32.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 79°F, so choose short-season varieties of Squash (Summer) to ensure they mature before fall.

Washburn County, WI (Zone 4a) Short season
131 days
Last Spring Frost May 17
131 growing days
First Fall Frost September 25

Washburn County Soil Profile

Soil Type

Silt Loam

Soil pH

6.1-6.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 2 Transplant: Jun 4 🍅 Harvest: Jul 23 – Sep 24
Recommended (50%) ✗ May not fit
Start indoors: Apr 5 Transplant: Jun 7 🍅 Harvest: Jul 26 – Sep 27
Safe Start (90%) ✗ May not fit
Start indoors: Apr 20 Transplant: Jun 22 🍅 Harvest: Aug 10 – Oct 12

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 Washburn County

How your county's soil matches Squash (Summer)'s growing requirements.

Soil pH

Your soil pH (6.1–6.9) is within Squash (Summer)'s preferred range (6.0–7.5).

Soil Texture

The silt loam soil in Washburn County is excellent for Squash (Summer) — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is excellent (4.3%) — Squash (Summer) will thrive.

How to Plant Squash (Summer)

1"
Planting Depth
30"
Between Plants
42"
Between Rows

Succession Planting Squash (Summer)

3
successive plantings in your 131-day season

Sow every 5.1 weeks. Last sowing by Jul 22 to harvest before frost.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
1.1″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Squash (Summer)

Squash (Summer) needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Squash (Summer) Needs Rainfall You Supplement Action
Jan 1.4" 0" ❄️ Dormant
Feb 1.2" 0" ❄️ Dormant
Mar 2.2" 0" ❄️ Dormant
Apr 3.5" 0" ❄️ Dormant
May 4.3" 3.7" 0.6" 💧 Light watering
Jun 4.3" 3.6" 0.7" 💧 Light watering
Jul 4.3" 4" 0.3" 💧 Light watering
Aug 4.3" 3.6" 0.7" 💧 Light watering
Sep 4.3" 3.1" 1.2" 💧 Light watering
Oct 2.7" 0" ❄️ Dormant
Nov 2.1" 0" ❄️ Dormant
Dec 1.6" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Washburn County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Squash (Summer) 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.

Squash (Summer) needs ~509 GDD — county provides 1,211 GDD Excellent fit

Squash (Summer) Planting Timeline — Washburn County, WI

Squash (Summer) Planting Calendar

Activity When Date Range
Start Indoors April 5 Apr 5 – Apr 19
Transplant Outdoors June 7 Jun 7 – Jun 21
Direct Sow May 31 May 31 – Jun 21
Harvest July 26 Jul 26 – Sep 27

Plant 1" deep · 30" apart · Rows 42" apart

Month-by-Month Timeline

MonthActivities
January
February
March
April Start Indoors
May Direct Sow
June Transplant Outdoors Direct Sow
July Harvest
August Harvest
September Harvest
October
November
December

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · Natural rainfall sufficient

📅 Days to Maturity

45–65 days

🧪 Soil pH

Needs 6–7.5 · Your soil: ideal

🗺️ USDA Zone

Zone 4a

📆 Growing Season

131 days in Washburn County

Growing Tips for Squash (Summer) in Washburn County

Direct sow Squash (Summer) outdoors after May 17 in Washburn County when soil has warmed and frost danger has passed.

Common pests for Squash (Summer) in this region include squash vine borer and cucumber beetles. Use row covers early in the season and inspect plants weekly.

General growing tips

Direct sow after last frost on mounds. Harvest frequently when fruits are 6-8 inches for best texture. Check plants daily as they grow rapidly in summer heat.

Companion Planting

Good Companions

Avoid Planting Near

  • Potatoes

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Squash (Summer) in Washburn County, WI?

Washburn County is in Zone 4a with an average last frost of May 17. Plan your Squash (Summer) planting based on this frost date — see the calendar above for exact timing.

What planting zone is Washburn County, WI?

Washburn County, Wisconsin is in USDA Hardiness Zone 4a. The average last spring frost is May 17 and first fall frost is September 25.

🌱

Your Washburn County Garden Planner — Free

A 24-page printable planner built for Washburn 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.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Washburn County, WI. Local conditions may vary. Last updated: May 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.