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When to Plant Thai Basil in Macomb County, MI

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.

Macomb County, Michigan is in USDA Zone 6a. The average last spring frost is April 28 and the first fall frost is October 20, giving you a growing season of approximately 175 days.

At an elevation of 628 feet, Macomb County receives approximately 33.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 91ยฐF, providing good warmth for Thai Basil during the growing season.

Macomb County, MI (Zone 6a) Moderate season
175 days
Last Spring Frost April 28
175 growing days
First Fall Frost October 20

Macomb County Soil Profile

Soil Type

Silt Loam

Soil pH

5.8-6.9

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (37 days to spare)
Start indoors: Mar 8 Transplant: May 10 🍅 Harvest: Jul 5 – Sep 6
Recommended (50%) ✓ Fits season (42 days to spare)
Start indoors: Mar 10 Transplant: May 12 🍅 Harvest: Jul 7 – Sep 8
Safe Start (90%) ✓ Fits season (38 days to spare)
Start indoors: Mar 25 Transplant: May 27 🍅 Harvest: Jul 22 – Sep 23

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.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
0.8″/week
You supply
0.2″/week
Watering frequency Only during dry spells
Season total 298 gal / 100 sq ft
Thai Basil needs ~1,141 GDD — county provides 3,193 GDD Excellent fit

Thai Basil Planting Timeline โ€” Macomb County, MI

Thai Basil Planting Calendar

Activity When Date Range
Start Indoors March 10 Mar 10 โ€“ Mar 24
Transplant Outdoors May 12 May 12 โ€“ May 26
Direct Sow May 5 May 5 โ€“ May 26
Harvest July 7 Jul 7 โ€“ Sep 8

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

Month-by-Month Timeline

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

Growing Conditions

Sun

Full Sun (6-8+ hours)

Water

Moderate โ€” regular watering

Days to Maturity

50โ€“75 days

Soil pH

6 โ€“ 7

USDA Zone

Zone 6a

Growing Season

175 days

Growing Tips for Macomb County

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

Level Up Your Garden

Frequently Asked Questions

When should I plant Thai Basil in Macomb County, MI?

Macomb County is in Zone 6a with an average last frost of April 28. Plan your Thai Basil planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Macomb County, MI?

Macomb County, Michigan is in USDA Hardiness Zone 6a. The average last spring frost is April 28 and first fall frost is October 20.

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Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Macomb County gardeners in Zone 6a organize planting dates, track what's growing, and never miss a planting window.

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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 Macomb County, MI. Local conditions may vary. Last updated: April 2026.