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When to Plant Rue in Blaine County, MT

Blaine County, Montana Zone 4a May

What to do in May

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

Avg. last frost May 14
Avg. first frost September 24
Soil temp (4") 31°F
Watering Moderate
Pest pressure Low
Daylight 15 hrs
  1. Plant out rue

    Plant tomatoes deep — bury the stem up to the first true leaves to grow extra roots. Everything else goes in at the same depth it grew in the tray.

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Rue is a bitter, aromatic perennial herb with bluish-green foliage used historically in medicine and as a pest deterrent. Handle with care as its sap can cause skin irritation.

Blaine County, Montana is in USDA Zone 4a. The average last spring frost is May 14 and the first fall frost is September 24, giving you a growing season of approximately 133 days.

At an elevation of 7,816 feet, Blaine County receives approximately 23.9 inches of rainfall annually with predominantly loam soil. Summer highs average 82°F, so choose short-season varieties of Rue to ensure they mature before fall.

Blaine County, MT (Zone 4a) Short season
133 days
Last Spring Frost May 14
133 growing days
First Fall Frost September 24
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Blaine County Soil Profile

Soil Type

Loam

Soil pH

6.4-7.7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Transplant: May 17 🍅 Harvest: Jul 26 – Sep 27
Recommended (50%) ✗ May not fit
Transplant: May 21 🍅 Harvest: Jul 30 – Oct 1
Safe Start (90%) ✗ May not fit
Transplant: Jun 3 🍅 Harvest: Aug 12 – Oct 14

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 Blaine County

How your county's soil matches Rue's growing requirements.

Soil pH

Your soil pH (6.4–7.7) overlaps with Rue's range (6.0–7.5), though not a perfect match.

Soil Texture

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

Drainage

Drainage is adequate for Rue.

Organic Matter

Organic matter is moderate (2.7%). Annual compost additions will help Rue.

How to Plant Rue

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

Succession Planting Rue

2
successive plantings in your 133-day season

Sow every 8 weeks. Last sowing by Jun 26 to harvest before frost.

Plant Water Budget

Plant needs
0.5″/week
Rainfall provides
0.8″/week
Watering frequency Natural rainfall sufficient
Season total 0 gal / 100 sq ft
Drought risk

Water stress score is 6/10 — consider drought-tolerant varieties and mulching

Monthly Watering Guide for Rue

Rue 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 Rue Needs Rainfall You Supplement Action
Jan 1.7" 0" ❄️ Dormant
Feb 1.5" 0" ❄️ Dormant
Mar 1.9" 0" ❄️ Dormant
Apr 2.4" 0" ❄️ Dormant
May 2.2" 3.2" 0" ✅ Rainfall sufficient
Jun 2.2" 1.6" 0.6" 💧 Light watering
Jul 2.2" 2.3" 0" ✅ Rainfall sufficient
Aug 2.2" 2.6" 0" ✅ Rainfall sufficient
Sep 2.2" 1.8" 0.4" 💧 Light watering
Oct 2" 0" ❄️ Dormant
Nov 1.6" 0" ❄️ Dormant
Dec 1.4" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Blaine County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.

Rue 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.

Rue needs ~920 GDD — county provides 1,529 GDD Excellent fit

Rue Planting Timeline — Blaine County, MT

Rue Planting Calendar

Activity When Date Range
Transplant Outdoors May 21 May 21 – Jun 4
Harvest July 30 Jul 30 – Oct 1

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

Month-by-Month Timeline

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

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.5"/week · Natural rainfall sufficient

📅 Days to Maturity

70–90 days

🧪 Soil pH

Needs 6–7.5 · Your soil: acceptable

🗺️ USDA Zone

Zone 4a

📆 Growing Season

133 days in Blaine County

Growing Tips for Rue in Blaine County

Direct sow Rue outdoors after May 14 in Blaine County when soil has warmed and frost danger has passed.

Blaine County receives only 24" of rain annually. Rue needs consistent moisture — install drip irrigation or water deeply 2-3 times per week.

General growing tips

Start seeds indoors or direct sow. Plant in well-drained soil. Wear gloves when handling as sap can cause phytophotodermatitis. Prune in early spring.

Companion Planting

Good Companions

Avoid Planting Near

  • Basil
  • Sage

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Rue in Blaine County, MT?

Blaine County is in Zone 4a with an average last frost of May 14. Plan your Rue planting based on this frost date — see the calendar above for exact timing.

What planting zone is Blaine County, MT?

Blaine County, Montana is in USDA Hardiness Zone 4a. The average last spring frost is May 14 and first fall frost is September 24.

🌱

Your Blaine County Garden Planner — Free

A 24-page printable planner built for Blaine 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.

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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 Blaine County, MT. 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.