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When to Plant Squash (Summer) in Sweet Grass County, MT

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

Sweet Grass County, Montana is in USDA Zone 4b. The average last spring frost is May 22 and the first fall frost is September 19, giving you a growing season of approximately 120 days.

At an elevation of 7,534 feet, Sweet Grass County receives approximately 16.9 inches of rainfall annually with predominantly loam soil. Summer highs average 82ยฐF, so choose short-season varieties of Squash (Summer) to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Squash (Summer) successfully. Mulch heavily to conserve soil moisture.

Sweet Grass County, MT (Zone 4b) Short season
120 days
Last Spring Frost May 22
120 growing days
First Fall Frost September 19

Sweet Grass County Soil Profile

Soil Type

Loam

Soil pH

6.7-8.4

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 4 Transplant: Jun 6 🍅 Harvest: Jul 25 – Sep 26
Recommended (50%) ✗ May not fit
Start indoors: Apr 10 Transplant: Jun 12 🍅 Harvest: Jul 31 – Oct 2
Safe Start (90%) ✗ May not fit
Start indoors: Apr 25 Transplant: Jun 27 🍅 Harvest: Aug 15 – Oct 17

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
0.6″/week
You supply
0.5″/week
Watering frequency 1-2 times/week
Season total 524 gal / 100 sq ft
Drought risk

Water stress score is 6/10 โ€” consider drought-tolerant varieties and mulching

Squash (Summer) needs ~632 GDD — county provides 1,380 GDD Excellent fit

Squash (Summer) Planting Timeline โ€” Sweet Grass County, MT

Squash (Summer) Planting Calendar

Activity When Date Range
Start Indoors April 10 Apr 10 โ€“ Apr 24
Transplant Outdoors June 12 Jun 12 โ€“ Jun 26
Direct Sow June 5 Jun 5 โ€“ Jun 26
Harvest July 31 Jul 31 โ€“ Oct 2

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 โ€”
June Transplant Outdoors Direct Sow
July Harvest
August Harvest
September Harvest
October Harvest
November โ€”
December โ€”

Growing Conditions

Sun

Full Sun (6-8+ hours)

Water

Moderate โ€” regular watering

Days to Maturity

45โ€“65 days

Soil pH

6 โ€“ 7.5

USDA Zone

Zone 4b

Growing Season

120 days

Growing Tips for Sweet Grass County

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

Level Up Your Garden

Frequently Asked Questions

When should I plant Squash (Summer) in Sweet Grass County, MT?

Sweet Grass County is in Zone 4b with an average last frost of May 22. Plan your Squash (Summer) planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Sweet Grass County, MT?

Sweet Grass County, Montana is in USDA Hardiness Zone 4b. The average last spring frost is May 22 and first fall frost is September 19.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Sweet Grass County gardeners in Zone 4b organize planting dates, track what's growing, and never miss a planting window.

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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 Sweet Grass County, MT. Local conditions may vary. Last updated: April 2026.