When to Plant Thai Basil in Clark County, IL
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.
Clark County, Illinois is in USDA Zone 6a. The average last spring frost is April 14 and the first fall frost is October 17, giving you a growing season of approximately 186 days.
At an elevation of 591 feet, Clark County receives approximately 41.4 inches of rainfall annually with predominantly silt loam soil. Summer highs average 90°F, providing good warmth for Thai Basil during the growing season.
Clark County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-6.8
Drainage
Well Drained
Plant Planting Risk Windows
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 Clark County
How your county's soil matches Thai Basil's growing requirements.
Soil pH
Your soil pH (6.2–6.8) is within Thai Basil's preferred range (6.0–7.0).
Soil Texture
The silt loam soil in Clark County is excellent for Thai Basil — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.9%) — Thai Basil will thrive.
How to Plant Thai Basil
Succession Planting Thai Basil
Sow every 5.7 weeks. Last sowing by Aug 03 to harvest before frost.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Thai Basil Planting Timeline — Clark County, IL
Thai Basil Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 24 | Feb 24 – Mar 10 |
| Transplant Outdoors | April 28 | Apr 28 – May 12 |
| Direct Sow | April 21 | Apr 21 – May 12 |
| Harvest | June 23 | Jun 23 – Aug 25 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | Start Indoors |
| March | Start Indoors |
| April | Transplant Outdoors Direct Sow |
| May | Transplant Outdoors Direct Sow |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | — |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
1"/week · Only during dry spells
📅 Days to Maturity
50–75 days
🧪 Soil pH
Needs 6–7 · Your soil: ideal
🗺️ USDA Zone
Zone 6a
📆 Growing Season
186 days in Clark County
Growing Tips for Thai Basil in Clark County
Direct sow Thai Basil outdoors after April 14 in Clark County when soil has warmed and frost danger has passed.
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
Level Up Your Garden
Thai Basil in Other Locations
Frequently Asked Questions
When should I plant Thai Basil in Clark County, IL?
Clark County is in Zone 6a with an average last frost of April 14. Plan your Thai Basil planting based on this frost date — see the calendar above for exact timing.
What planting zone is Clark County, IL?
Clark County, Illinois is in USDA Hardiness Zone 6a. The average last spring frost is April 14 and first fall frost is October 17.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Clark County gardeners in Zone 6a organize planting dates, track what's growing, and never miss a planting window.
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