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When to Plant Butternut Squash in Niobrara County, WY

Niobrara County, Wyoming Zone 5a May

May in the garden — Niobrara County, Wyoming

May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Niobrara County, Wyoming.

Avg. last frost May 15
Avg. first frost September 21
Soil temp (4") 40°F
Watering High
Pest pressure Low
Daylight 14.5 hrs
  1. Get butternut squash in the ground

    Harden off for 7 days — a little more sun each day — before planting. That's the difference between a seedling that thrives and one that stalls.

  2. Outdoor sowing time: butternut squash

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

Looking ahead to June
  • Starting indoors: butternut squash

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Butternut squash is a popular winter squash with a long neck, small seed cavity, and sweet, nutty orange flesh. It stores exceptionally well for months.

Niobrara County, Wyoming is in USDA Zone 5a. The average last spring frost is May 15 and the first fall frost is September 21, giving you a growing season of approximately 129 days.

At an elevation of 5,262 feet, Niobrara County receives approximately 19.5 inches of rainfall annually with predominantly loam soil. Summer highs average 82°F, so choose short-season varieties of Butternut Squash to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Butternut Squash successfully. Mulch heavily to conserve soil moisture.

Niobrara County, WY (Zone 5a) Short season
129 days
Last Spring Frost May 15
129 growing days
First Fall Frost September 21
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Niobrara County Soil Profile

Soil Type

Loam

Soil pH

6.2-7.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 8 Transplant: May 27 🍅 Harvest: Aug 26 – Sep 30
Recommended (50%) ✗ May not fit
Start indoors: Apr 10 Transplant: May 29 🍅 Harvest: Aug 28 – Oct 2
Safe Start (90%) ✗ May not fit
Start indoors: Apr 30 Transplant: Jun 18 🍅 Harvest: Sep 17 – Oct 22

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 Niobrara County

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

Soil pH

Your soil pH (6.2–7.9) is more alkaline than Butternut Squash prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.2%). Annual compost additions will help Butternut Squash.

How to Plant Butternut Squash

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

Plant Water Budget

Plant needs
1.1″/week
Rainfall provides
0.6″/week
You supply
0.6″/week
Watering frequency 1-2 times/week
Season total 641 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Butternut Squash

Butternut 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 Butternut Squash Needs Rainfall You Supplement Action
Jan 1.2" 0" ❄️ Dormant
Feb 1.2" 0" ❄️ Dormant
Mar 1.8" 0" ❄️ Dormant
Apr 2.1" 0" ❄️ Dormant
May 4.8" 2.2" 2.6" 🚿 Regular watering
Jun 4.8" 1.3" 3.5" 🚿 Regular watering
Jul 4.8" 1.8" 3" 🚿 Regular watering
Aug 4.8" 2.1" 2.7" 🚿 Regular watering
Sep 4.8" 1.5" 3.3" 🚿 Regular watering
Oct 1.7" 0" ❄️ Dormant
Nov 1.5" 0" ❄️ Dormant
Dec 1.1" 0" ❄️ Dormant

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

Butternut 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.

Butternut Squash needs ~1,121 GDD — county provides 1,483 GDD Excellent fit

Butternut Squash Planting Timeline — Niobrara County, WY

Butternut Squash Planting Calendar

Activity When Date Range
Start Indoors April 10 Apr 10 – Apr 24
Transplant Outdoors May 29 May 29 – Jun 12
Direct Sow May 22 May 22 – Jun 12
Harvest August 28 Aug 28 – Oct 2

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
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Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1.1"/week · 1-2 times/week

📅 Days to Maturity

85–110 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 5a

📆 Growing Season

129 days in Niobrara County

Growing Tips for Butternut Squash in Niobrara County

Direct sow Butternut Squash outdoors after May 15 in Niobrara County when soil has warmed and frost danger has passed.

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

Niobrara County receives only 20" of rain annually. Butternut Squash needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Start seeds indoors 3 weeks early or direct sow after frost. Allow 6-8 feet for sprawling vines. Harvest when the skin is hard and uniformly tan. Cure in the sun for 10 days.

Companion Planting

Good Companions

Avoid Planting Near

  • Potatoes

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Butternut Squash in Niobrara County, WY?

Niobrara County is in Zone 5a with an average last frost of May 15. Plan your Butternut Squash planting based on this frost date — see the calendar above for exact timing.

What planting zone is Niobrara County, WY?

Niobrara County, Wyoming is in USDA Hardiness Zone 5a. The average last spring frost is May 15 and first fall frost is September 21.

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Your Niobrara County Garden Planner — Free

A 24-page printable planner built for Niobrara County (Zone 5a). 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 Niobrara County, WY. 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.