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When to Plant Acorn Squash in Missoula County, MT

Missoula County, Montana Zone 5b May

Missoula County, Montana gardeners: here's your May plan

Your garden in Missoula County, Montana is working on a schedule, even when you're not. Here's where you should be this May.

Avg. last frost May 14
Avg. first frost September 23
Soil temp (4") 32°F
Watering High
Pest pressure Low
Daylight 14.9 hrs
  1. Get acorn squash in the ground

    Plant tomatoes deep — bury the stem up to the first true leaves to grow extra roots. Everything else goes in at the same depth it grew in the tray.

  2. Seed acorn squash outdoors

    Rake a smooth bed, make a shallow furrow, drop seeds at the spacing on the packet, water gently, walk away.

June prep starts now
  • Starting indoors: acorn squash

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Acorn squash is a small winter squash with dark green, ribbed skin and mildly sweet orange flesh. It is perfect for stuffing and roasting as individual servings.

Missoula County, Montana is in USDA Zone 5b. The average last spring frost is May 14 and the first fall frost is September 23, giving you a growing season of approximately 132 days.

At an elevation of 8,019 feet, Missoula County receives approximately 15.9 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Acorn Squash during the growing season. With low rainfall, drip irrigation is essential for growing Acorn Squash successfully. Mulch heavily to conserve soil moisture.

Missoula County, MT (Zone 5b) Short season
132 days
Last Spring Frost May 14
132 growing days
First Fall Frost September 23

Missoula County Soil Profile

Soil Type

Loam

Soil pH

6.2-7.7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (1 days to spare)
Start indoors: Apr 3 Transplant: May 22 🍅 Harvest: Aug 14 – Sep 18
Recommended (50%) ✗ May not fit
Start indoors: Apr 9 Transplant: May 28 🍅 Harvest: Aug 20 – Sep 24
Safe Start (90%) ✗ May not fit
Start indoors: Apr 30 Transplant: Jun 18 🍅 Harvest: Sep 10 – Oct 15

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 Missoula County

How your county's soil matches Acorn Squash's growing requirements.

Soil pH

Your soil pH (6.2–7.7) overlaps with Acorn Squash's range (5.5–7.0), though not a perfect match.

Soil Texture

The loam soil in Missoula County is excellent for Acorn Squash — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.5%). Annual compost additions will help Acorn Squash.

How to Plant Acorn Squash

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

Plant Water Budget

Plant needs
1.1″/week
Rainfall provides
0.5″/week
You supply
0.7″/week
Watering frequency 2-3 times/week
Season total 838 gal / 100 sq ft
Drought risk

Water stress score is 8/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Acorn Squash

Acorn 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 Acorn Squash Needs Rainfall You Supplement Action
Jan 1" 0" ❄️ Dormant
Feb 1" 0" ❄️ Dormant
Mar 1.6" 0" ❄️ Dormant
Apr 1.7" 0" ❄️ Dormant
May 4.8" 1.7" 3.1" 🚿 Regular watering
Jun 4.8" 1.1" 3.7" 🚿 Regular watering
Jul 4.8" 1.3" 3.5" 🚿 Regular watering
Aug 4.8" 1.9" 2.9" 🚿 Regular watering
Sep 4.8" 1.4" 3.4" 🚿 Regular watering
Oct 1.5" 0" ❄️ Dormant
Nov 1" 0" ❄️ Dormant
Dec 1" 0" ❄️ Dormant

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

Acorn 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.

Acorn Squash needs ~1,372 GDD — county provides 2,013 GDD Excellent fit

Acorn Squash Planting Timeline — Missoula County, MT

Acorn Squash Planting Calendar

Activity When Date Range
Start Indoors April 9 Apr 9 – Apr 23
Transplant Outdoors May 28 May 28 – Jun 11
Direct Sow May 21 May 21 – Jun 11
Harvest August 20 Aug 20 – Sep 24

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
November
December

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1.1"/week · 2-3 times/week

📅 Days to Maturity

80–100 days

🧪 Soil pH

Needs 5.5–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 5b

📆 Growing Season

132 days in Missoula County

Growing Tips for Acorn Squash in Missoula County

Direct sow Acorn Squash outdoors after May 14 in Missoula County when soil has warmed and frost danger has passed.

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

Missoula County receives only 16" of rain annually. Acorn Squash needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Direct sow after last frost. Harvest when the ground spot turns orange and the skin is hard. Acorn squash has a shorter storage life than butternut, lasting about 2 months.

Companion Planting

Good Companions

Avoid Planting Near

  • Potatoes

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Acorn Squash in Missoula County, MT?

Missoula County is in Zone 5b with an average last frost of May 14. Plan your Acorn Squash planting based on this frost date — see the calendar above for exact timing.

What planting zone is Missoula County, MT?

Missoula County, Montana is in USDA Hardiness Zone 5b. The average last spring frost is May 14 and first fall frost is September 23.

🌱

Your Missoula County Garden Planner — Free

A 24-page printable planner built for Missoula 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 Missoula County, MT. 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.