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When to Plant Squash (Winter) in Boundary County, ID

Boundary County, Idaho Zone 5b April

Boundary County, Idaho gardeners: here's your April plan

Each item below is timed to Boundary County, Idaho's frost dates and soil temperatures. Skip nothing, stress about nothing.

Avg. last frost May 10
Avg. first frost September 22
Soil temp (4") 29°F
Watering High
Pest pressure Low
Daylight 13.5 hrs
May prep starts now
  • Transplants going out: squash (winter)
  • Direct-sowing: squash (winter)

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Winter squash includes butternut, acorn, delicata, and hubbard varieties grown to full maturity with hard rinds for storage. They develop sweet, dense flesh.

Boundary County, Idaho is in USDA Zone 5b. The average last spring frost is May 10 and the first fall frost is September 22, giving you a growing season of approximately 135 days.

At an elevation of 5,105 feet, Boundary County receives approximately 21.1 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Squash (Winter) during the growing season.

Boundary County, ID (Zone 5b) Short season
135 days
Last Spring Frost May 10
135 growing days
First Fall Frost September 22

Boundary County Soil Profile

Soil Type

Loam

Soil pH

6.7-8.3

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 27 Transplant: May 15 🍅 Harvest: Aug 7 – Oct 2
Recommended (50%) ✗ May not fit
Start indoors: Apr 5 Transplant: May 24 🍅 Harvest: Aug 16 – Oct 11
Safe Start (90%) ✗ May not fit
Start indoors: Apr 30 Transplant: Jun 18 🍅 Harvest: Sep 10 – Nov 5

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 Boundary County

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

Soil pH

Your soil pH (6.7–8.3) is more alkaline than Squash (Winter) prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.3%). Annual compost additions will help Squash (Winter).

How to Plant Squash (Winter)

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

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.7″/week
You supply
0.4″/week
Watering frequency 1-2 times/week
Season total 495 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Squash (Winter)

Squash (Winter) 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 (Winter) Needs Rainfall You Supplement Action
Jan 1.6" 0" ❄️ Dormant
Feb 1.2" 0" ❄️ Dormant
Mar 1.9" 0" ❄️ Dormant
Apr 2" 0" ❄️ Dormant
May 4.3" 2.7" 1.6" 💧 Light watering
Jun 4.3" 1.6" 2.7" 🚿 Regular watering
Jul 4.3" 1.8" 2.5" 🚿 Regular watering
Aug 4.3" 1.9" 2.4" 🚿 Regular watering
Sep 4.3" 1.6" 2.7" 🚿 Regular watering
Oct 2.1" 0" ❄️ Dormant
Nov 1.5" 0" ❄️ Dormant
Dec 1.3" 0" ❄️ Dormant

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

Squash (Winter) 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 (Winter) needs ~1,525 GDD — county provides 2,058 GDD Excellent fit

Squash (Winter) Planting Timeline — Boundary County, ID

Squash (Winter) Planting Calendar

Activity When Date Range
Start Indoors April 5 Apr 5 – Apr 19
Transplant Outdoors May 24 May 24 – Jun 7
Direct Sow May 17 May 17 – Jun 7
Harvest August 16 Aug 16 – Oct 11

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

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · 1-2 times/week

📅 Days to Maturity

80–120 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 5b

📆 Growing Season

135 days in Boundary County

Growing Tips for Squash (Winter) in Boundary County

Direct sow Squash (Winter) outdoors after May 10 in Boundary County when soil has warmed and frost danger has passed.

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

Boundary County receives only 21" of rain annually. Squash (Winter) needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Direct sow after last frost on rich mounds. Allow ample space for sprawling vines. Cure harvested fruits in the sun for 10 days before storing in a cool, dry place.

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 (Winter) in Boundary County, ID?

Boundary County is in Zone 5b with an average last frost of May 10. Plan your Squash (Winter) planting based on this frost date — see the calendar above for exact timing.

What planting zone is Boundary County, ID?

Boundary County, Idaho is in USDA Hardiness Zone 5b. The average last spring frost is May 10 and first fall frost is September 22.

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Your Boundary County Garden Planner — Free

A 24-page printable planner built for Boundary 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.

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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 Boundary County, ID. Local conditions may vary. Last updated: April 2026.

Sources & credits

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