When to Plant Thyme in Petroleum County, MT
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.
Petroleum County, Montana is in USDA Zone 4a. The average last spring frost is May 18 and the first fall frost is September 24, giving you a growing season of approximately 129 days.
At an elevation of 8,358 feet, Petroleum County receives approximately 13.7 inches of rainfall annually with predominantly loam soil. Summer highs average 81°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.
Petroleum County Soil Profile
Soil Type
Loam
Soil pH
6.8-8.2
Drainage
Well Drained
Plant Planting Risk Windows
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
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Thyme Planting Timeline — Petroleum County, MT
Thyme Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 25 | May 25 – Jun 8 |
| Harvest | August 3 | Aug 3 – Oct 5 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Transplant Outdoors |
| June | Transplant Outdoors |
| July | — |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
Sun
Full Sun (6-8+ hours)
Water
Low — drought tolerant
Days to Maturity
70–90 days
Soil pH
6 – 8
USDA Zone
Zone 4a
Growing Season
129 days
Growing Tips for Petroleum 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
Thyme in Other Locations
Frequently Asked Questions
When should I plant Thyme in Petroleum County, MT?
Petroleum County is in Zone 4a with an average last frost of May 18. Plan your Thyme planting based on this frost date — see the calendar above for exact timing.
What planting zone is Petroleum County, MT?
Petroleum County, Montana is in USDA Hardiness Zone 4a. The average last spring frost is May 18 and first fall frost is September 24.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Petroleum County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.
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