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When to Plant Mustard Greens in Missoula County, MT

Missoula County, Montana Zone 5a April

This month in Missoula County, Montana

Each item below is timed to Missoula County, Montana's frost dates and soil temperatures. Skip nothing, stress about nothing.

Avg. last frost May 14
Avg. first frost September 23
Soil temp (4") 20°F
Watering High
Pest pressure Low
Daylight 13.4 hrs
  1. Scatter mustard greens into prepared beds

    Keep the top inch of soil moist until germination — a gentle morning watering for 5–7 days does the job.

Coming up in May — start thinking about
  • Transplants going out: mustard greens

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Mustard greens are fast-growing brassicas with a spicy, peppery kick. They come in green, red, and purple varieties and are excellent cooked or in salads.

Missoula County, Montana is in USDA Zone 5a. The average last spring frost is May 14 and the first fall frost is September 23, giving you a growing season of approximately 132 days.

At an elevation of 8,019 feet, Missoula County receives approximately 15.9 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Mustard Greens during the growing season. With low rainfall, drip irrigation is essential for growing Mustard Greens successfully. Mulch heavily to conserve soil moisture.

Missoula County, MT (Zone 5a) Short season
132 days
Last Spring Frost May 14
132 growing days
First Fall Frost September 23

Missoula County Soil Profile

Soil Type

Loam

Soil pH

6.2-7.7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (36 days to spare)
Start indoors: Apr 3 Transplant: May 8 🍅 Harvest: Jun 12 – Aug 14
Recommended (50%) ✓ Fits season (34 days to spare)
Start indoors: Apr 9 Transplant: May 14 🍅 Harvest: Jun 18 – Aug 20
Safe Start (90%) ✓ Fits season (33 days to spare)
Start indoors: Apr 30 Transplant: Jun 4 🍅 Harvest: Jul 9 – Sep 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 Missoula County

How your county's soil matches Mustard Greens's growing requirements.

Soil pH

Your soil pH (6.2–7.7) overlaps with Mustard Greens's range (6.0–7.0), though not a perfect match.

Soil Texture

The loam soil in Missoula County is excellent for Mustard Greens — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

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

How to Plant Mustard Greens

0.5"
Planting Depth
6"
Between Plants
12"
Between Rows

Fall planting: Sow 10 weeks before your first frost date for a fall harvest.

Succession Planting Mustard Greens

5
successive plantings in your 132-day season

Sow every 3.4 weeks. Last sowing by Aug 04 to harvest before frost.

For a dedicated fall crop, sow by Jul 15.

Plant Water Budget

Plant needs
0.7″/week
Rainfall provides
0.5″/week
You supply
0.2″/week
Watering frequency Only during dry spells
Season total 274 gal / 100 sq ft
Drought risk

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

Monthly Watering Guide for Mustard Greens

Mustard Greens needs approximately 0.7 inches of water per week (3" per month). Here's how your county's rainfall compares month by month.

Month Mustard Greens Needs Rainfall You Supplement Action
Jan 1" 0" ❄️ Dormant
Feb 1" 0" ❄️ Dormant
Mar 1.6" 0" ❄️ Dormant
Apr 1.7" 0" ❄️ Dormant
May 3" 1.7" 1.3" 💧 Light watering
Jun 3" 1.1" 1.9" 🚿 Regular watering
Jul 3" 1.3" 1.7" 🚿 Regular watering
Aug 3" 1.9" 1.1" 💧 Light watering
Sep 3" 1.4" 1.6" 🚿 Regular watering
Oct 1.5" 0" ❄️ Dormant
Nov 1" 0" ❄️ Dormant
Dec 1" 0" ❄️ Dormant

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

Mustard Greens 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.

Mustard Greens needs ~610 GDD — county provides 2,013 GDD Excellent fit

Mustard Greens Planting Timeline — Missoula County, MT

Mustard Greens Planting Calendar

Activity When Date Range
Start Indoors April 9 Apr 9 – Apr 23
Transplant Outdoors May 14 May 14 – May 28
Direct Sow April 30 Apr 30 – May 21
Harvest June 18 Jun 18 – Aug 20
Fall Sowing July 15 Jul 15 – Jul 29

Plant 0.5" deep · 6" apart · Rows 12" apart

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Partial Shade (3-6 hours)

💧 Water

0.7"/week · Only during dry spells

📅 Days to Maturity

30–50 days

🧪 Soil pH

Needs 6–7 · Your soil: acceptable

🗺️ USDA Zone

Zone 5a

📆 Growing Season

132 days in Missoula County

Growing Tips for Mustard Greens in Missoula County

Direct sow Mustard Greens outdoors after May 14 in Missoula County when soil has warmed and frost danger has passed.

Your generous 132.0-day season in Missoula County allows multiple plantings of Mustard Greens. Sow every 15.0 days for continuous harvest.

Common pests for Mustard Greens in this region include cabbage worm and flea beetles. Use row covers early in the season and inspect plants weekly.

General growing tips

Direct sow in early spring or fall. Harvest young leaves for milder flavor. Plants bolt quickly in heat so grow as a cool-season crop or provide shade.

Companion Planting

Good Companions

Avoid Planting Near

  • Strawberries

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Mustard Greens in Missoula County, MT?

Missoula County is in Zone 5a with an average last frost of May 14. Plan your Mustard Greens planting based on this frost date — see the calendar above for exact timing.

What planting zone is Missoula County, MT?

Missoula County, Montana is in USDA Hardiness Zone 5a. The average last spring frost is May 14 and first fall frost is September 23.

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Your Missoula County Garden Planner — Free

A 24-page printable planner built for Missoula 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 Missoula County, MT. Local conditions may vary. Last updated: April 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.