When to Plant Thai Basil in Union 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.
Union County, Illinois is in USDA Zone 6b. The average last spring frost is April 10 and the first fall frost is October 21, giving you a growing season of approximately 194 days.
At an elevation of 1,017 feet, Union County receives approximately 34.2 inches of rainfall annually with predominantly silt loam soil. Summer highs average 88°F, providing good warmth for Thai Basil during the growing season.
Union County Soil Profile
Soil Type
Silt Loam
Soil pH
5.8-7.1
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.
Plant Water Budget
Thai Basil Planting Timeline — Union County, IL
Thai Basil Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Start Indoors | February 20 | Feb 20 – Mar 6 |
| Transplant Outdoors | April 24 | Apr 24 – May 8 |
| Direct Sow | April 17 | Apr 17 – May 8 |
| Harvest | June 19 | Jun 19 – Aug 21 |
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
Moderate — regular watering
Days to Maturity
50–75 days
Soil pH
6 – 7
USDA Zone
Zone 6b
Growing Season
194 days
Growing Tips for Union 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
Level Up Your Garden
Thai Basil in Other Locations
Frequently Asked Questions
When should I plant Thai Basil in Union County, IL?
Union County is in Zone 6b with an average last frost of April 10. Plan your Thai Basil planting based on this frost date — see the calendar above for exact timing.
What planting zone is Union County, IL?
Union County, Illinois is in USDA Hardiness Zone 6b. The average last spring frost is April 10 and first fall frost is October 21.
Plan Your Garden with Confidence
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