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When to Plant Thai Basil in Mineral County, CO

Thai basil has a distinctive anise-licorice flavor with sturdy purple stems and small leaves. It is essential in Thai, Vietnamese, and other Southeast Asian cuisines.

Mineral County, Colorado is in USDA Zone 4a. The average last spring frost is June 10 and the first fall frost is September 13, giving you a growing season of approximately 95 days.

At an elevation of 7,809 feet, Mineral County receives approximately 12.8 inches of rainfall annually with predominantly loam soil. Summer highs average 80ยฐF, so choose short-season varieties of Thai Basil to ensure they mature before fall. With low rainfall, drip irrigation is essential for growing Thai Basil successfully. Mulch heavily to conserve soil moisture.

Mineral County, CO (Zone 4a) Very short season
95 days
Last Spring Frost June 10
95 growing days
First Fall Frost September 13

Mineral County Soil Profile

Soil Type

Loam

Soil pH

6.8-8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 3 Transplant: Jun 19 🍅 Harvest: Aug 14 – Oct 16
Recommended (50%) ✗ May not fit
Start indoors: Apr 15 Transplant: Jul 1 🍅 Harvest: Aug 26 – Oct 28
Safe Start (90%) ✗ May not fit
Start indoors: May 1 Transplant: Jul 17 🍅 Harvest: Sep 11 – Nov 13

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 Mineral County

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

Soil pH

Your soil pH (6.8โ€“8.0) is more alkaline than Thai Basil prefers (6.0โ€“7.0). Add sulfur or peat moss to lower pH.

Soil Texture

The loam soil in Mineral County is excellent for Thai Basil โ€” good drainage, moisture retention, and nutrient holding capacity.

Drainage

Drainage is adequate for Thai Basil.

Organic Matter

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

How to Plant Thai Basil

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

Succession Planting Thai Basil

2
successive plantings in your 95-day season

Sow every 5.7 weeks. Last sowing by Jun 30 to harvest before frost.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.6″/week
You supply
0.9″/week
Watering frequency 2-3 times/week
Season total 745 gal / 100 sq ft
Drought risk

Water stress score is 6/10 โ€” consider drought-tolerant varieties and mulching

Monthly Watering Guide for Thai Basil

Thai Basil needs approximately 1 inches of water per week (4.3" per month). Here's how your county's rainfall compares month by month.

Month Thai Basil Needs Rainfall You Supplement Action
Jan โ€” 1" 0" โ„๏ธ Dormant
Feb โ€” 0.8" 0" โ„๏ธ Dormant
Mar โ€” 1.2" 0" โ„๏ธ Dormant
Apr โ€” 1.1" 0" โ„๏ธ Dormant
May โ€” 1.6" 0" โ„๏ธ Dormant
Jun 4.3" 0.8" 3.5" ๐Ÿšฟ Regular watering
Jul 4.3" 1" 3.3" ๐Ÿšฟ Regular watering
Aug 4.3" 1.4" 2.9" ๐Ÿšฟ Regular watering
Sep 4.3" 0.9" 3.4" ๐Ÿšฟ Regular watering
Oct โ€” 1.2" 0" โ„๏ธ Dormant
Nov โ€” 0.9" 0" โ„๏ธ Dormant
Dec โ€” 0.8" 0" โ„๏ธ Dormant

Water needs are for active growing months only (Junโ€“Sep in Mineral County). Supplement amounts are based on average rainfall โ€” actual needs vary with temperature, soil, and mulching.

Thai 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" โ€” every day above 50ยฐF 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.

Thai Basil needs ~625 GDD — county provides 950 GDD Excellent fit

Thai Basil Planting Timeline โ€” Mineral County, CO

Thai Basil Planting Calendar

Activity When Date Range
Start Indoors April 15 Apr 15 โ€“ Apr 29
Transplant Outdoors July 1 Jul 1 โ€“ Jul 15
Direct Sow June 17 Jun 17 โ€“ Jul 8
Harvest August 26 Aug 26 โ€“ Oct 28

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

Month-by-Month Timeline

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

Growing Conditions

โ˜€๏ธ Sun

Full Sun (6-8+ hours)

๐Ÿ’ง Water

1"/week ยท 2-3 times/week

๐Ÿ“… Days to Maturity

50โ€“75 days

๐Ÿงช Soil pH

Needs 6โ€“7 ยท Your soil: too_alkaline

๐Ÿ—บ๏ธ USDA Zone

Zone 4a

๐Ÿ“† Growing Season

95 days in Mineral County

Growing Tips for Thai Basil in Mineral County

Direct sow Thai Basil outdoors after June 10 in Mineral County when soil has warmed and frost danger has passed.

Mineral County receives only 13" of rain annually. Thai Basil needs consistent moisture โ€” install drip irrigation or water deeply 2-3 times per week.

General growing tips

Start seeds indoors or direct sow after last frost. Thai basil holds up better to heat in cooking than sweet basil. Pinch flowers to prolong leaf production.

Companion Planting

Good Companions

Avoid Planting Near

  • Rue
  • Sage

Check more plant combinations with our Companion Planting Checker →

Frequently Asked Questions

When should I plant Thai Basil in Mineral County, CO?

Mineral County is in Zone 4a with an average last frost of June 10. Plan your Thai Basil planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Mineral County, CO?

Mineral County, Colorado is in USDA Hardiness Zone 4a. The average last spring frost is June 10 and first fall frost is September 13.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Mineral County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.

Get Your Free Garden Planner →

Free download. Plan your entire garden season in minutes.

Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for Mineral County, CO. Local conditions may vary. Last updated: April 2026.