When to Plant Yarrow in Petroleum County, MT
This month in Petroleum County, Montana
Your Petroleum County, Montana garden is entering a new phase. Here's what's on the schedule for April and why each task matters now.
Before May arrives, get these ready
- Transplants going out: yarrow
Yarrow is a drought-tolerant perennial herb with feathery foliage and flat-topped flower clusters in white, yellow, pink, or red. It attracts beneficial insects and is used in herbal medicine.
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 Yarrow to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Yarrow 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.
Soil Compatibility in Petroleum County
How your county's soil matches Yarrow's growing requirements.
Soil pH
Your soil pH (6.8–8.2) is more alkaline than Yarrow prefers (5.5–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Petroleum County is excellent for Yarrow — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Yarrow.
Organic Matter
Organic matter is moderate (2.7%). Annual compost additions will help Yarrow.
How to Plant Yarrow
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Yarrow
Yarrow needs approximately 0.5 inches of water per week (2.2" per month). Here's how your county's rainfall compares month by month.
| Month | Yarrow Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.1" | 0" | ❄️ Dormant |
| Feb | — | 0.7" | 0" | ❄️ Dormant |
| Mar | — | 1.2" | 0" | ❄️ Dormant |
| Apr | — | 1.3" | 0" | ❄️ Dormant |
| May | 2.2" | 1.8" | 0.4" | 💧 Light watering |
| Jun | 2.2" | 0.9" | 1.3" | 🚿 Regular watering |
| Jul | 2.2" | 1.2" | 1" | 💧 Light watering |
| Aug | 2.2" | 1.5" | 0.7" | 💧 Light watering |
| Sep | 2.2" | 1.2" | 1" | 💧 Light watering |
| Oct | — | 1.2" | 0" | ❄️ Dormant |
| Nov | — | 1" | 0" | ❄️ Dormant |
| Dec | — | 0.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Petroleum County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Yarrow 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.
Yarrow Planting Timeline — Petroleum County, MT
Yarrow Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 25 | May 25 – Jun 8 |
| Harvest | August 24 | Aug 24 – Oct 19 |
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
0.5"/week · Only during dry spells
📅 Days to Maturity
90–120 days
🧪 Soil pH
Needs 5.5–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 4a
📆 Growing Season
129 days in Petroleum County
Growing Tips for Yarrow in Petroleum County
Direct sow Yarrow outdoors after May 18 in Petroleum County when soil has warmed and frost danger has passed.
Your 129.0-day growing season in Petroleum County is tight for Yarrow (90.0-120.0 days to maturity). Start indoors and choose early-maturing varieties.
Common pests for Yarrow in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
Petroleum County receives only 14" of rain annually. Yarrow needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.
General growing tips
Direct sow or start from divisions. Yarrow thrives in poor soil and is very drought-tolerant. Deadhead to encourage reblooming. Divide clumps every 3 years.
Companion Planting
Good Companions
Check more plant combinations with our Companion Planting Checker →
Yarrow in Other Locations
Frequently Asked Questions
When should I plant Yarrow in Petroleum County, MT?
Petroleum County is in Zone 4a with an average last frost of May 18. Plan your Yarrow 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.
Your Petroleum County Garden Planner — Free
A 24-page printable planner built for Petroleum County (Zone 4a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.