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When to Plant Basil in Golden Valley County, MT

Golden Valley County, Montana Zone 4b May

What to do in May

Your Golden Valley County, Montana garden is entering a new phase. Here's what's on the schedule for May and why each task matters now.

Avg. last frost May 22
Avg. first frost September 20
Soil temp (4") 30°F
Watering Moderate
Pest pressure Low
Daylight 14.8 hrs
  1. Plant basil from seed, right in the garden

    Mark the row. Birds and stray feet both have opinions about unmarked beds.

Coming up in June — start thinking about
  • Transplants going out: 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.

Golden Valley County, Montana is in USDA Zone 4b. The average last spring frost is May 22 and the first fall frost is September 20, giving you a growing season of approximately 121 days.

At an elevation of 7,917 feet, Golden Valley County receives approximately 25 inches of rainfall annually with predominantly loam soil. Summer highs average 83°F, so choose short-season varieties of Basil to ensure they mature before fall.

Golden Valley County, MT (Zone 4b) Short season
121 days
Last Spring Frost May 22
121 growing days
First Fall Frost September 20

Golden Valley County Soil Profile

Soil Type

Loam

Soil pH

6.8-8.3

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Mar 23 Transplant: Jun 8 🍅 Harvest: Aug 3 – Oct 5
Recommended (50%) ✗ May not fit
Start indoors: Mar 27 Transplant: Jun 12 🍅 Harvest: Aug 7 – Oct 9
Safe Start (90%) ✗ May not fit
Start indoors: Apr 12 Transplant: Jun 28 🍅 Harvest: Aug 23 – Oct 25

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 Golden Valley County

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

Soil pH

Your soil pH (6.8–8.3) is more alkaline than Basil prefers (6.0–7.0). Add sulfur or peat moss to lower pH.

Soil Texture

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

Organic Matter

Organic matter is moderate (2.2%). Annual compost additions will help Basil.

How to Plant Basil

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

Succession Planting Basil

2
successive plantings in your 121-day season

Sow every 5.7 weeks. Last sowing by Jul 07 to harvest before frost.

Plant Water Budget

Plant needs
0.6″/week
Rainfall provides
0.9″/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 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 2" 0" ❄️ Dormant
Feb 1.3" 0" ❄️ Dormant
Mar 2.1" 0" ❄️ Dormant
Apr 2.6" 0" ❄️ Dormant
May 2.6" 3" 0" ✅ Rainfall sufficient
Jun 2.6" 1.9" 0.7" 💧 Light watering
Jul 2.6" 2.3" 0.3" 💧 Light watering
Aug 2.6" 2.4" 0.2" 💧 Light watering
Sep 2.6" 1.9" 0.7" 💧 Light watering
Oct 2.4" 0" ❄️ Dormant
Nov 1.7" 0" ❄️ Dormant
Dec 1.3" 0" ❄️ Dormant

Water needs are for active growing months only (May–Sep in Golden Valley 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 ~766 GDD — county provides 1,482 GDD Excellent fit

Basil Planting Timeline — Golden Valley 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

MonthActivities
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 · Natural rainfall sufficient

📅 Days to Maturity

50–75 days

🧪 Soil pH

Needs 6–7 · Your soil: too_alkaline

🗺️ USDA Zone

Zone 4b

📆 Growing Season

121 days in Golden Valley County

Growing Tips for Basil in Golden Valley County

Direct sow Basil outdoors after May 22 in Golden Valley 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 Golden Valley County, MT?

Golden Valley County is in Zone 4b 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 Golden Valley County, MT?

Golden Valley County, Montana is in USDA Hardiness Zone 4b. The average last spring frost is May 22 and first fall frost is September 20.

🌱

Your Golden Valley County Garden Planner — Free

A 24-page printable planner built for Golden Valley County (Zone 4b). 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 Golden Valley 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.