When to Plant Basil in Glacier County, MT
Basil is a fragrant warm-season herb essential to Italian and Thai cuisines. It comes in many varieties including sweet, Thai, purple, and lemon types.
Glacier County, Montana is in USDA Zone 4a. The average last spring frost is May 22 and the first fall frost is September 18, giving you a growing season of approximately 119 days.
At an elevation of 8,147 feet, Glacier County receives approximately 13.3 inches of rainfall annually with predominantly loam soil. Summer highs average 80°F, so choose short-season varieties of Basil to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Basil successfully. Mulch heavily to conserve soil moisture.
Glacier County Soil Profile
Soil Type
Loam
Soil pH
6.3-8.1
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 Glacier County
How your county's soil matches Basil's growing requirements.
Soil pH
Your soil pH (6.3–8.1) is more alkaline than Basil prefers (6.0–7.0). Add sulfur or peat moss to lower pH.
Soil Texture
The loam soil in Glacier County is excellent for Basil — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.4%). Annual compost additions will help Basil.
How to Plant Basil
Succession Planting Basil
Sow every 5.7 weeks. Last sowing by Jul 05 to harvest before frost.
Plant Water Budget
Water stress score is 8/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Basil
Basil needs approximately 0.6 inches of water per week (2.6" per month). Here's how your county's rainfall compares month by month.
| Month | Basil Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 0.8" | 0" | ❄️ Dormant |
| Feb | — | 0.8" | 0" | ❄️ Dormant |
| Mar | — | 1" | 0" | ❄️ Dormant |
| Apr | — | 1.3" | 0" | ❄️ Dormant |
| May | 2.6" | 1.6" | 1" | 💧 Light watering |
| Jun | 2.6" | 1" | 1.6" | 🚿 Regular watering |
| Jul | 2.6" | 1.3" | 1.3" | 🚿 Regular watering |
| Aug | 2.6" | 1.4" | 1.2" | 💧 Light watering |
| Sep | 2.6" | 1.1" | 1.5" | 🚿 Regular watering |
| Oct | — | 1.3" | 0" | ❄️ Dormant |
| Nov | — | 1" | 0" | ❄️ Dormant |
| Dec | — | 0.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Glacier County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Basil 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.
Basil Planting Timeline — Glacier County, MT
Basil Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | March 27 | Mar 27 – Apr 10 |
| Transplant Outdoors | June 12 | Jun 12 – Jun 26 |
| Direct Sow | May 29 | May 29 – Jun 19 |
| Harvest | August 7 | Aug 7 – Oct 9 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | Start Indoors |
| April | Start Indoors |
| May | Direct Sow |
| June | Transplant Outdoors Direct Sow |
| July | — |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.6"/week · Only during dry spells
📅 Days to Maturity
50–75 days
🧪 Soil pH
Needs 6–7 · Your soil: too_alkaline
🗺️ USDA Zone
Zone 4a
📆 Growing Season
119 days in Glacier County
Growing Tips for Basil in Glacier County
Direct sow Basil outdoors after May 22 in Glacier County when soil has warmed and frost danger has passed.
General growing tips
Start seeds indoors or direct sow after last frost. Pinch flower buds to extend leaf production. Harvest leaves from the top down, cutting just above a leaf pair.
Companion Planting
Good Companions
Avoid Planting Near
Check more plant combinations with our Companion Planting Checker →
Isolate 150 ft between varieties. Different basil species can cross.
Basil in Other Locations
Frequently Asked Questions
When should I plant Basil in Glacier County, MT?
Glacier County is in Zone 4a with an average last frost of May 22. Plan your Basil planting based on this frost date — see the calendar above for exact timing.
What planting zone is Glacier County, MT?
Glacier County, Montana is in USDA Hardiness Zone 4a. The average last spring frost is May 22 and first fall frost is September 18.
Plan Your Garden with Confidence
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