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When to Plant Thyme in Fremont County, CO

Thyme is a low-growing perennial herb with tiny, aromatic leaves and a warm, earthy flavor. It is one of the most versatile culinary and medicinal herbs.

Fremont County, Colorado is in USDA Zone 5b. The average last spring frost is May 23 and the first fall frost is September 25, giving you a growing season of approximately 125 days.

At an elevation of 6,575 feet, Fremont County receives approximately 18.5 inches of rainfall annually with predominantly loam soil. Summer highs average 84ยฐF, so choose short-season varieties of Thyme to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Thyme successfully. Mulch heavily to conserve soil moisture.

Fremont County, CO (Zone 5b) Short season
125 days
Last Spring Frost May 23
125 growing days
First Fall Frost September 25

Fremont County Soil Profile

Soil Type

Loam

Soil pH

6.7-8.3

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Transplant: May 18 🍅 Harvest: Jul 27 – Sep 28
Recommended (50%) ✗ May not fit
Transplant: May 30 🍅 Harvest: Aug 8 – Oct 10
Safe Start (90%) ✗ May not fit
Transplant: Jun 22 🍅 Harvest: Aug 31 – Nov 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
0.5″/week
Rainfall provides
0.6″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft
Drought risk

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

Thyme needs ~1,040 GDD — county provides 1,625 GDD Excellent fit

Thyme Planting Timeline โ€” Fremont County, CO

Thyme Planting Calendar

Activity When Date Range
Transplant Outdoors May 30 May 30 โ€“ Jun 13
Harvest August 8 Aug 8 โ€“ Oct 10

Plant 0.5" deep ยท 8" apart ยท Rows 12" apart

Month-by-Month Timeline

MonthActivities
January โ€”
February โ€”
March โ€”
April โ€”
May Transplant Outdoors
June Transplant Outdoors
July โ€”
August Harvest
September Harvest
October Harvest
November โ€”
December โ€”

Growing Conditions

Sun

Full Sun (6-8+ hours)

Water

Low โ€” drought tolerant

Days to Maturity

70โ€“90 days

Soil pH

6 โ€“ 8

USDA Zone

Zone 5b

Growing Season

125 days

Growing Tips for Fremont County

Start from seed, cuttings, or divisions. Plant in well-drained, lean soil. Prune lightly after flowering. Replace plants every 3-4 years when they become woody.

Companion Planting

Good Companions

Level Up Your Garden

Frequently Asked Questions

When should I plant Thyme in Fremont County, CO?

Fremont County is in Zone 5b with an average last frost of May 23. Plan your Thyme planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Fremont County, CO?

Fremont County, Colorado is in USDA Hardiness Zone 5b. The average last spring frost is May 23 and first fall frost is September 25.

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Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Fremont County gardeners in Zone 5b 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 Fremont County, CO. Local conditions may vary. Last updated: April 2026.