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When to Plant Kidney Beans in Carbon County, MT

Carbon County, Montana Zone 5a May

May in Carbon County, Montana — your action list

A quick May briefing for Carbon County, Montana gardeners — what's urgent, what's next, and what can wait.

Avg. last frost May 13
Avg. first frost September 28
Soil temp (4") 36°F
Watering High
Pest pressure Low
Daylight 14.7 hrs
  1. Direct-sow kidney beans

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

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Kidney beans are a popular dry bean variety named for their shape, available in red and white types. They are the classic bean for chili and red beans and rice.

Carbon County, Montana is in USDA Zone 5a. The average last spring frost is May 13 and the first fall frost is September 28, giving you a growing season of approximately 138 days.

At an elevation of 5,849 feet, Carbon County receives approximately 23.3 inches of rainfall annually with predominantly loam soil. Summer highs average 83°F, so choose short-season varieties of Kidney Beans to ensure they mature before fall.

Carbon County, MT (Zone 5a) Short season
138 days
Last Spring Frost May 13
138 growing days
First Fall Frost September 28

Carbon County Soil Profile

Soil Type

Loam

Soil pH

6.8-8.1

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (10 days to spare)
Transplant: May 7 🍅 Harvest: Aug 6 – Sep 10
Recommended (50%) ✓ Fits season (12 days to spare)
Transplant: May 13 🍅 Harvest: Aug 12 – Sep 16
Safe Start (90%) ✓ Fits season (0 days to spare)
Transplant: Jun 10 🍅 Harvest: Sep 9 – Oct 14

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 Carbon County

How your county's soil matches Kidney Beans's growing requirements.

Soil pH

Your soil pH (6.8–8.1) overlaps with Kidney Beans's range (6.0–7.5), though not a perfect match.

Soil Texture

The loam soil in Carbon County is excellent for Kidney Beans — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.3%). Annual compost additions will help Kidney Beans.

How to Plant Kidney Beans

1"
Planting Depth
15"
Between Plants
24"
Between Rows

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.7″/week
You supply
0.4″/week
Watering frequency 1-2 times/week
Season total 429 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Kidney Beans

Kidney Beans needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Kidney Beans Needs Rainfall You Supplement Action
Jan 1.9" 0" ❄️ Dormant
Feb 1.5" 0" ❄️ Dormant
Mar 2.3" 0" ❄️ Dormant
Apr 2.6" 0" ❄️ Dormant
May 4.3" 2.4" 1.9" 💧 Light watering
Jun 4.3" 1.9" 2.4" 🚿 Regular watering
Jul 4.3" 2" 2.3" 🚿 Regular watering
Aug 4.3" 2.2" 2.1" 💧 Light watering
Sep 4.3" 1.8" 2.5" 🚿 Regular watering
Oct 2.2" 0" ❄️ Dormant
Nov 1.4" 0" ❄️ Dormant
Dec 1.3" 0" ❄️ Dormant

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

Kidney Beans 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.

Kidney Beans needs ~1,194 GDD — county provides 1,690 GDD Excellent fit

Kidney Beans Planting Timeline — Carbon County, MT

Kidney Beans Planting Calendar

Activity When Date Range
Direct Sow May 20 May 20 – Jun 10
Harvest August 19 Aug 19 – Sep 23

Plant 1" deep · 15" apart · Rows 24" apart

Month-by-Month Timeline

MonthActivities
January
February
March
April
May Direct Sow
June Direct Sow
July
August Harvest
September Harvest
October
November
December

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

1"/week · 1-2 times/week

📅 Days to Maturity

85–110 days

🧪 Soil pH

Needs 6–7.5 · Your soil: acceptable

🗺️ USDA Zone

Zone 5a

📆 Growing Season

138 days in Carbon County

Growing Tips for Kidney Beans in Carbon County

Direct sow Kidney Beans outdoors after May 13 in Carbon County when soil has warmed and frost danger has passed.

Common pests for Kidney Beans in this region include bean beetles and aphids. Use row covers early in the season and inspect plants weekly.

Carbon County receives only 23" of rain annually. Kidney Beans needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Direct sow after frost. Allow pods to dry completely on the plant. Kidney beans must be thoroughly cooked as raw or undercooked beans contain harmful lectins.

Companion Planting

Good Companions

Avoid Planting Near

  • Onion
  • Garlic

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Kidney Beans in Carbon County, MT?

Carbon County is in Zone 5a with an average last frost of May 13. Plan your Kidney Beans planting based on this frost date — see the calendar above for exact timing.

What planting zone is Carbon County, MT?

Carbon County, Montana is in USDA Hardiness Zone 5a. The average last spring frost is May 13 and first fall frost is September 28.

🌱

Your Carbon County Garden Planner — Free

A 24-page printable planner built for Carbon 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 Carbon 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.