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When to Plant Thyme in Carbon County, WY

Carbon County, Wyoming Zone 5a May

Your May planting checklist for Carbon County, Wyoming

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

Avg. last frost May 31
Avg. first frost September 18
Soil temp (4") 30°F
Watering High
Pest pressure Low
Daylight 14.4 hrs
Coming up in June — start thinking about
  • Transplants going out: thyme

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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.

Carbon County, Wyoming is in USDA Zone 5a. The average last spring frost is May 31 and the first fall frost is September 18, giving you a growing season of approximately 110 days.

At an elevation of 8,469 feet, Carbon County receives approximately 15.2 inches of rainfall annually with predominantly loam soil. Summer highs average 80°F, 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.

Carbon County, WY (Zone 5a) Short season
110 days
Last Spring Frost May 31
110 growing days
First Fall Frost September 18

Carbon 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: Jun 2 🍅 Harvest: Aug 11 – Oct 13
Recommended (50%) ✗ May not fit
Transplant: Jun 7 🍅 Harvest: Aug 16 – Oct 18
Safe Start (90%) ✗ May not fit
Transplant: Jun 19 🍅 Harvest: Aug 28 – Oct 30

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 Thyme's growing requirements.

Soil pH

Your soil pH (6.7–8.3) overlaps with Thyme's range (6.0–8.0), though not a perfect match.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.8%). Annual compost additions will help Thyme.

How to Plant Thyme

0.5"
Planting Depth
8"
Between Plants
12"
Between Rows

Plant Water Budget

Plant needs
0.3″/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 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Thyme

Thyme needs approximately 0.3 inches of water per week (1.3" per month). Here's how your county's rainfall compares month by month.

Month Thyme Needs Rainfall You Supplement Action
Jan 1.2" 0" ❄️ Dormant
Feb 1" 0" ❄️ Dormant
Mar 1.5" 0" ❄️ Dormant
Apr 1.5" 0" ❄️ Dormant
May 1.3" 2" 0" ✅ Rainfall sufficient
Jun 1.3" 1.1" 0.2" 💧 Light watering
Jul 1.3" 1.3" 0" ✅ Rainfall sufficient
Aug 1.3" 1.5" 0" ✅ Rainfall sufficient
Sep 1.3" 1.1" 0.2" 💧 Light watering
Oct 1.2" 0" ❄️ Dormant
Nov 1" 0" ❄️ Dormant
Dec 0.9" 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.

Thyme 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.

Thyme needs ~800 GDD — county provides 1,100 GDD Excellent fit

Thyme Planting Timeline — Carbon County, WY

Thyme Planting Calendar

Activity When Date Range
Transplant Outdoors June 7 Jun 7 – Jun 21
Harvest August 16 Aug 16 – Oct 18

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

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.3"/week · Natural rainfall sufficient

📅 Days to Maturity

70–90 days

🧪 Soil pH

Needs 6–8 · Your soil: acceptable

🗺️ USDA Zone

Zone 5a

📆 Growing Season

110 days in Carbon County

Growing Tips for Thyme in Carbon County

Direct sow Thyme outdoors after May 31 in Carbon County when soil has warmed and frost danger has passed.

General growing tips

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

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Thyme in Carbon County, WY?

Carbon County is in Zone 5a with an average last frost of May 31. Plan your Thyme planting based on this frost date — see the calendar above for exact timing.

What planting zone is Carbon County, WY?

Carbon County, Wyoming is in USDA Hardiness Zone 5a. The average last spring frost is May 31 and first fall frost is September 18.

🌱

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, WY. 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.