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When to plant Basil in Silver Bow County, MT

In Silver Bow County, Basil is a single-season spring crop — there's no second fall window. Plant June 22–July 13 for an 50–75-day harvest, finishing well before the September 7 first frost.

When to Plant Basil in Silver Bow County, MT

Basil
Silver Bow County, Montana Zone 5a August

Your August planting checklist for Silver Bow County, Montana

We've pulled the most time-sensitive tasks for Silver Bow County, Montana this August and put them front and centre. Tackle them in order.

Avg. last frost June 15
Avg. first frost September 7
Soil temp (4") 60°F
Watering High
Pest pressure High
Daylight 14 hrs
  1. Fire up the seed-starting tray: basil

    Bottom-water once the first true leaves appear — it keeps stems dry and knocks back damping-off.

  2. Pick basil

    Morning harvests are best — cooler temperatures mean crisper produce and longer fridge life.

A few tasks this August that'll pay off in September
  • First harvests: basil

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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.

Silver Bow County, Montana is in USDA Zone 5a. The average last spring frost is June 15 and the first fall frost is September 7, giving you a growing season of approximately 84 days.

At an elevation of 5,305 feet, Silver Bow County receives approximately 14.3 inches of rainfall annually with predominantly loam soil. Summer highs average 84°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.

Silver Bow County, MT (Zone 5a) Very short season
84 days
Last Spring Frost June 15
84 growing days
First Fall Frost September 7

Silver Bow County Soil Profile

Soil Type

Loam

Soil pH

6.6-8.3

Drainage

Well Drained

Basil Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 21 Transplant: Jun 23 🍅 Harvest: Aug 18 – Oct 20
Recommended (50%) ✗ May not fit
Start indoors: Apr 27 Transplant: Jun 29 🍅 Harvest: Aug 24 – Oct 26
Safe Start (90%) ✗ May not fit
Start indoors: May 5 Transplant: Jul 7 🍅 Harvest: Sep 1 – Nov 3

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 Silver Bow County

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

Soil pH

Your soil pH (6.6–8.3) is more alkaline than Basil prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

The loam soil in Silver Bow County is excellent for Basil — good drainage, moisture retention, and nutrient holding capacity.

Organic Matter

Organic matter is moderate (2.5%). Annual compost additions will help Basil.

How to Plant Basil

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

Basil Water Budget

Plant needs
0.6″/week
Rainfall provides
0.7″/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 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 1.1" 0" ❄️ Dormant
Feb 1" 0" ❄️ Dormant
Mar 1.3" 0" ❄️ Dormant
Apr 1.4" 0" ❄️ Dormant
May 1.5" 0" ❄️ Dormant
Jun 2.6" 0.9" 1.7" 🚿 Regular watering
Jul 2.6" 1.1" 1.5" 🚿 Regular watering
Aug 2.6" 1.8" 0.8" 💧 Light watering
Sep 2.6" 1.1" 1.5" 🚿 Regular watering
Oct 1.1" 0" ❄️ Dormant
Nov 1" 0" ❄️ Dormant
Dec 0.9" 0" ❄️ Dormant

Water needs are for active growing months only (Jun–Sep in Silver Bow 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 needs ~812 GDD — county provides 1,092 GDD Excellent fit

Basil Planting Timeline — Silver Bow County, MT

Basil Planting Calendar

Activity When Date Range
Start Indoors April 27 Apr 27 – May 11
Transplant Outdoors June 29 Jun 29 – Jul 13
Direct Sow June 22 Jun 22 – Jul 13
Harvest August 24 Aug 24 – Oct 26

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

Month-by-Month Timeline

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

Growing Conditions

☀️ Sun

Full Sun (6-8+ hours)

💧 Water

0.6"/week · Natural rainfall sufficient

📅 Days to Maturity

50–75 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 5a

📆 Growing Season

84 days in Silver Bow County

Growing Tips for Basil in Silver Bow County

Direct sow Basil outdoors after June 15 in Silver Bow 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

  • Rue
  • Sage

Check more plant combinations with our Companion Planting Checker →

🌾 Save Your Own Basil Seeds
Life Cycle Annual
Pollination Self-Pollinating
How to Collect Let flower spikes dry brown on the plant.
Storage Store airtight; viable 5 years at 35°F, under 45% humidity.

Isolate 150 ft between varieties. Different basil species can cross.

Frequently Asked Questions

When should I plant Basil in Silver Bow County, MT?

Silver Bow County is in Zone 5a with an average last frost of June 15. Plan your Basil planting based on this frost date — see the calendar above for exact timing.

What planting zone is Silver Bow County, MT?

Silver Bow County, Montana is in USDA Hardiness Zone 5a. The average last spring frost is June 15 and first fall frost is September 7.

When should I plant Basil in Silver Bow County, MT?

In Silver Bow County, MT, plant Basil after the last frost (around June 15) and before the first frost (around September 7). Best results when soil holds above 50°F.

What growing zone is Silver Bow County, MT for Basil?

Silver Bow County sits in USDA Zone 5a. Basil grows reliably in zones 4a through 11b, so it's a good fit here.

Can Basil grow in Silver Bow County's climate?

Yes — Basil grows well in Silver Bow County's temperate climate. Silver Bow County averages a 84-day frost-free season, with last frost around June 15 and first frost around September 7.

🌱

Your Silver Bow County Garden Planner — Free

A 22-page printable planner built for Silver Bow 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 Silver Bow County, MT. Local conditions may vary. Last updated: August 2026.

Sources & credits

Every number on this page traces back to a primary horticulture or government data source. Click through to verify.