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When to Plant Mustard Greens in Big Horn County, WY

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.

Big Horn County, Wyoming is in USDA Zone 4a. The average last spring frost is May 9 and the first fall frost is October 2, giving you a growing season of approximately 146 days.

At an elevation of 7,668 feet, Big Horn County receives approximately 13.7 inches of rainfall annually with predominantly loam soil. Summer highs average 84ยฐF, so choose short-season varieties of Mustard Greens to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Mustard Greens successfully. Mulch heavily to conserve soil moisture.

Big Horn County, WY (Zone 4a) Short season
146 days
Last Spring Frost May 9
146 growing days
First Fall Frost October 2

Big Horn 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 (42 days to spare)
Start indoors: Mar 23 Transplant: May 4 🍅 Harvest: Jun 8 – Aug 10
Recommended (50%) ✓ Fits season (48 days to spare)
Start indoors: Mar 28 Transplant: May 9 🍅 Harvest: Jun 13 – Aug 15
Safe Start (90%) ✓ Fits season (51 days to spare)
Start indoors: Apr 7 Transplant: May 19 🍅 Harvest: Jun 23 – Aug 25

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
0.4″/week
You supply
0.7″/week
Watering frequency 2-3 times/week
Season total 945 gal / 100 sq ft
Drought risk

Water stress score is 8/10 โ€” consider drought-tolerant varieties and mulching

Mustard Greens needs ~520 GDD — county provides 1,898 GDD Excellent fit

Mustard Greens Planting Timeline โ€” Big Horn County, WY

Mustard Greens Planting Calendar

Activity When Date Range
Start Indoors March 28 Mar 28 โ€“ Apr 11
Transplant Outdoors May 9 May 9 โ€“ May 23
Direct Sow May 2 May 2 โ€“ May 23
Fall Sowing July 10 Jul 10 โ€“ Jul 24
Harvest June 13 Jun 13 โ€“ Aug 15

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

Month-by-Month Timeline

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

Growing Conditions

Sun

Partial Shade (3-6 hours)

Water

Moderate โ€” regular watering

Days to Maturity

30โ€“50 days

Soil pH

6 โ€“ 7

USDA Zone

Zone 4a

Growing Season

146 days

Growing Tips for Big Horn County

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

Level Up Your Garden

Frequently Asked Questions

When should I plant Mustard Greens in Big Horn County, WY?

Big Horn County is in Zone 4a with an average last frost of May 9. Plan your Mustard Greens planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Big Horn County, WY?

Big Horn County, Wyoming is in USDA Hardiness Zone 4a. The average last spring frost is May 9 and first fall frost is October 2.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Big Horn County gardeners in Zone 4a 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 Big Horn County, WY. Local conditions may vary. Last updated: April 2026.