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When to Plant Pumpkin in Flathead County, MT

Pumpkins are large-fruited squash varieties grown for eating, decoration, and seed production. They require ample space and a long, warm growing season.

Flathead County, Montana is in USDA Zone 5a. The average last spring frost is June 3 and the first fall frost is September 10, giving you a growing season of approximately 99 days.

At an elevation of 6,233 feet, Flathead County receives approximately 20.7 inches of rainfall annually with predominantly loam soil. Summer highs average 87ยฐF, providing good warmth for Pumpkin during the growing season.

Flathead County, MT (Zone 5a) Very short season
99 days
Last Spring Frost June 3
99 growing days
First Fall Frost September 10

Flathead County Soil Profile

Soil Type

Loam

Soil pH

6.6-8.4

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 17 Transplant: Jun 5 🍅 Harvest: Sep 4 – Oct 23
Recommended (50%) ✗ May not fit
Start indoors: Apr 29 Transplant: Jun 17 🍅 Harvest: Sep 16 – Nov 4
Safe Start (90%) ✗ May not fit
Start indoors: May 18 Transplant: Jul 6 🍅 Harvest: Oct 5 – Nov 23

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.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.9″/week
You supply
0.2″/week
Watering frequency Only during dry spells
Season total 129 gal / 100 sq ft
Drought risk

Water stress score is 8/10 โ€” consider drought-tolerant varieties and mulching

Pumpkin needs ~1,563 GDD — county provides 1,509 GDD Tight fit

Pumpkin Planting Timeline โ€” Flathead County, MT

Pumpkin Planting Calendar

Activity When Date Range
Start Indoors April 29 Apr 29 โ€“ May 13
Transplant Outdoors June 17 Jun 17 โ€“ Jul 1
Direct Sow June 10 Jun 10 โ€“ Jul 1
Harvest September 16 Sep 16 โ€“ Nov 4

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

Month-by-Month Timeline

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

Growing Conditions

Sun

Full Sun (6-8+ hours)

Water

Moderate โ€” regular watering

Days to Maturity

85โ€“120 days

Soil pH

6 โ€“ 7.5

USDA Zone

Zone 5a

Growing Season

99 days

Growing Tips for Flathead County

Direct sow on mounds after last frost. Allow 6-10 feet between plants. Slip a board under developing fruit to prevent rot. Harvest when rind is hard and deep in color.

Companion Planting

Good Companions

Avoid Planting Near

  • Potatoes

Level Up Your Garden

Frequently Asked Questions

When should I plant Pumpkin in Flathead County, MT?

Flathead County is in Zone 5a with an average last frost of June 3. Plan your Pumpkin planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Flathead County, MT?

Flathead County, Montana is in USDA Hardiness Zone 5a. The average last spring frost is June 3 and first fall frost is September 10.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Flathead County gardeners in Zone 5a organize planting dates, track what's growing, and never miss a planting window.

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Free download. Plan your entire garden season in minutes.

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