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When to Plant Mustard Greens in Park County, CO

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.

Park County, Colorado is in USDA Zone 4b. The average last spring frost is June 16 and the first fall frost is September 4, giving you a growing season of approximately 80 days.

At an elevation of 7,567 feet, Park County receives approximately 23.3 inches of rainfall annually with predominantly loam soil. Summer highs average 83ยฐF, so choose short-season varieties of Mustard Greens to ensure they mature before fall.

Park County, CO (Zone 4b) Very short season
80 days
Last Spring Frost June 16
80 growing days
First Fall Frost September 4

Park County Soil Profile

Soil Type

Loam

Soil pH

6.2-7.6

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 29 Transplant: Jun 10 🍅 Harvest: Jul 15 – Sep 16
Recommended (50%) ✗ May not fit
Start indoors: May 5 Transplant: Jun 16 🍅 Harvest: Jul 21 – Sep 22
Safe Start (90%) ✗ May not fit
Start indoors: May 15 Transplant: Jun 26 🍅 Harvest: Jul 31 – Oct 2

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
1.2″/week
You supply
0.1″/week
Watering frequency Only during dry spells
Season total 66 gal / 100 sq ft
Drought risk

Water stress score is 6/10 โ€” consider drought-tolerant varieties and mulching

Mustard Greens needs ~490 GDD — county provides 980 GDD Excellent fit

Mustard Greens Planting Timeline โ€” Park County, CO

Mustard Greens Planting Calendar

Activity When Date Range
Start Indoors May 5 May 5 โ€“ May 19
Transplant Outdoors June 16 Jun 16 โ€“ Jun 30
Direct Sow June 9 Jun 9 โ€“ Jun 30
Fall Sowing June 12 Jun 12 โ€“ Jun 26
Harvest July 21 Jul 21 โ€“ Sep 22

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

Month-by-Month Timeline

MonthActivities
January โ€”
February โ€”
March โ€”
April โ€”
May Start Indoors
June Transplant Outdoors Direct Sow Fall Sowing
July Harvest
August Harvest
September Harvest
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 4b

Growing Season

80 days

Growing Tips for Park 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 Park County, CO?

Park County is in Zone 4b with an average last frost of June 16. Plan your Mustard Greens planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Park County, CO?

Park County, Colorado is in USDA Hardiness Zone 4b. The average last spring frost is June 16 and first fall frost is September 4.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Park County gardeners in Zone 4b organize planting dates, track what's growing, and never miss a planting window.

Get Your Free Garden Planner →

Free download. Plan your entire garden season in minutes.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Park County, CO. Local conditions may vary. Last updated: April 2026.