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When to Plant Pumpkin in Cassia County, ID

Cassia County, Idaho Zone 6b May

Top priorities for Cassia County, Idaho gardeners in May

May is a pivotal month for Cassia County, Idaho gardens. Focus on these tasks first and you'll set up the rest of the season for success.

Avg. last frost May 15
Avg. first frost October 1
Soil temp (4") 35°F
Watering High
Pest pressure Low
Daylight 14.4 hrs
  1. Move pumpkin from tray to bed

    Frost risk is low now in Cassia County, Idaho. If you've been covering beds overnight, you can stop.

  2. Plant pumpkin from seed, right in the garden

    Your soil is 35°F — warm enough for these to germinate without babying.

To set up a strong June, finish these tasks
  • Starting indoors: pumpkin

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

Cassia County, Idaho is in USDA Zone 6b. The average last spring frost is May 15 and the first fall frost is October 1, giving you a growing season of approximately 139 days.

At an elevation of 8,089 feet, Cassia County receives approximately 17.5 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Pumpkin during the growing season. With low rainfall, drip irrigation is essential for growing Pumpkin successfully. Mulch heavily to conserve soil moisture.

Cassia County, ID (Zone 6b) Short season
139 days
Last Spring Frost May 15
139 growing days
First Fall Frost October 1

Cassia County Soil Profile

Soil Type

Loam

Soil pH

6.3-8.2

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 4 Transplant: May 23 🍅 Harvest: Aug 22 – Oct 10
Recommended (50%) ✗ May not fit
Start indoors: Apr 10 Transplant: May 29 🍅 Harvest: Aug 28 – Oct 16
Safe Start (90%) ✗ May not fit
Start indoors: May 5 Transplant: Jun 23 🍅 Harvest: Sep 22 – Nov 10

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 Cassia County

How your county's soil matches Pumpkin's growing requirements.

Soil pH

Your soil pH (6.3–8.2) overlaps with Pumpkin's range (6.0–7.5), though not a perfect match.

Soil Texture

The loam soil in Cassia County is excellent for Pumpkin — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

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

How to Plant Pumpkin

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

Plant Water Budget

Plant needs
1.3″/week
Rainfall provides
0.5″/week
You supply
0.9″/week
Watering frequency 2-3 times/week
Season total 1,145 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Pumpkin

Pumpkin needs approximately 1.3 inches of water per week (5.6" per month). Here's how your county's rainfall compares month by month.

Month Pumpkin Needs Rainfall You Supplement Action
Jan 1.1" 0" ❄️ Dormant
Feb 1" 0" ❄️ Dormant
Mar 1.7" 0" ❄️ Dormant
Apr 1.8" 0" ❄️ Dormant
May 5.6" 2.3" 3.3" 🚿 Regular watering
Jun 5.6" 1.1" 4.5" 🚿 Regular watering
Jul 5.6" 1.5" 4.1" 🚿 Regular watering
Aug 5.6" 1.7" 3.9" 🚿 Regular watering
Sep 5.6" 1.3" 4.3" 🚿 Regular watering
Oct 5.6" 1.6" 4" 🚿 Regular watering
Nov 1.1" 0" ❄️ Dormant
Dec 1.1" 0" ❄️ Dormant

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

Pumpkin 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.

Pumpkin needs ~1,563 GDD — county provides 2,119 GDD Excellent fit

Pumpkin Planting Timeline — Cassia County, ID

Pumpkin 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 16

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

1.3"/week · 2-3 times/week

📅 Days to Maturity

85–120 days

🧪 Soil pH

Needs 6–7.5 · Your soil: acceptable

🗺️ USDA Zone

Zone 6b

📆 Growing Season

139 days in Cassia County

Growing Tips for Pumpkin in Cassia County

Direct sow Pumpkin outdoors after May 15 in Cassia County when soil has warmed and frost danger has passed.

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

Cassia County receives only 18" of rain annually. Pumpkin needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

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

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Pumpkin in Cassia County, ID?

Cassia County is in Zone 6b with an average last frost of May 15. Plan your Pumpkin planting based on this frost date — see the calendar above for exact timing.

What planting zone is Cassia County, ID?

Cassia County, Idaho is in USDA Hardiness Zone 6b. The average last spring frost is May 15 and first fall frost is October 1.

🌱

Your Cassia County Garden Planner — Free

A 24-page printable planner built for Cassia County (Zone 6b). 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 Cassia County, ID. 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.