Blog

When to Plant Tarragon in DeWitt County, IL

French tarragon is a perennial herb with slender leaves and a distinctive anise-like flavor essential in French cooking. It does not produce viable seed and must be propagated vegetatively.

DeWitt County, Illinois is in USDA Zone 5b. The average last spring frost is April 15 and the first fall frost is October 17, giving you a growing season of approximately 185 days.

At an elevation of 801 feet, DeWitt County receives approximately 31.8 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84ยฐF, so choose short-season varieties of Tarragon to ensure they mature before fall.

DeWitt County, IL (Zone 5b) Moderate season
185 days
Last Spring Frost April 15
185 growing days
First Fall Frost October 17

DeWitt County Soil Profile

Soil Type

Silt Loam

Soil pH

6.1-7

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (44 days to spare)
Transplant: Apr 17 🍅 Harvest: Jun 19 – Aug 28
Recommended (50%) ✓ Fits season (45 days to spare)
Transplant: Apr 22 🍅 Harvest: Jun 24 – Sep 2
Safe Start (90%) ✓ Fits season (47 days to spare)
Transplant: May 5 🍅 Harvest: Jul 7 – Sep 15

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
0.7″/week
You supply
0.6″/week
Watering frequency 1-2 times/week
Season total 952 gal / 100 sq ft
Tarragon needs ~975 GDD — county provides 2,405 GDD Excellent fit

Tarragon Planting Timeline โ€” DeWitt County, IL

Tarragon Planting Calendar

Activity When Date Range
Transplant Outdoors April 22 Apr 22 โ€“ May 6
Harvest June 24 Jun 24 โ€“ Sep 2

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

Month-by-Month Timeline

MonthActivities
January โ€”
February โ€”
March โ€”
April Transplant Outdoors
May Transplant Outdoors
June Harvest
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

60โ€“90 days

Soil pH

6 โ€“ 7.5

USDA Zone

Zone 5b

Growing Season

185 days

Growing Tips for DeWitt County

Purchase plants or divisions as French tarragon does not grow true from seed. Plant in well-drained soil. Divide every 3-4 years to maintain vigor. Harvest tips regularly for best flavor.

Companion Planting

Good Companions

Level Up Your Garden

Frequently Asked Questions

When should I plant Tarragon in DeWitt County, IL?

DeWitt County is in Zone 5b with an average last frost of April 15. Plan your Tarragon planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is DeWitt County, IL?

DeWitt County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 15 and first fall frost is October 17.

๐ŸŒฑ

Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help DeWitt County gardeners in Zone 5b 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 DeWitt County, IL. Local conditions may vary. Last updated: April 2026.