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When to Plant Thai Basil in Fond du Lac County, WI

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.

Fond du Lac County, Wisconsin is in USDA Zone 4b. The average last spring frost is April 27 and the first fall frost is October 14, giving you a growing season of approximately 170 days.

At an elevation of 713 feet, Fond du Lac County receives approximately 32.9 inches of rainfall annually with predominantly silt loam soil. Summer highs average 80ยฐF, so choose short-season varieties of Thai Basil to ensure they mature before fall.

Fond du Lac County, WI (Zone 4b) Moderate season
170 days
Last Spring Frost April 27
170 growing days
First Fall Frost October 14

Fond du Lac County Soil Profile

Soil Type

Silt Loam

Soil pH

6.2-7.2

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (28 days to spare)
Start indoors: Feb 26 Transplant: May 14 🍅 Harvest: Jul 9 – Sep 10
Recommended (50%) ✓ Fits season (30 days to spare)
Start indoors: Mar 2 Transplant: May 18 🍅 Harvest: Jul 13 – Sep 14
Safe Start (90%) ✓ Fits season (28 days to spare)
Start indoors: Mar 17 Transplant: Jun 2 🍅 Harvest: Jul 28 – Sep 29

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 283 gal / 100 sq ft
Thai Basil needs ~625 GDD — county provides 1,700 GDD Excellent fit

Thai Basil Planting Timeline โ€” Fond du Lac County, WI

Thai Basil Planting Calendar

Activity When Date Range
Start Indoors March 2 Mar 2 โ€“ Mar 16
Transplant Outdoors May 18 May 18 โ€“ Jun 1
Direct Sow May 4 May 4 โ€“ May 25
Harvest July 13 Jul 13 โ€“ Sep 14

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 Transplant Outdoors
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 4b

Growing Season

170 days

Growing Tips for Fond du Lac 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 Fond du Lac County, WI?

Fond du Lac County is in Zone 4b with an average last frost of April 27. Plan your Thai Basil planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Fond du Lac County, WI?

Fond du Lac County, Wisconsin is in USDA Hardiness Zone 4b. The average last spring frost is April 27 and first fall frost is October 14.

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Plan Your Garden with Confidence

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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 Fond du Lac County, WI. Local conditions may vary. Last updated: April 2026.