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When to Plant Tarragon in Douglas 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.

Douglas County, Illinois is in USDA Zone 5b. 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 1,036 feet, Douglas County receives approximately 30.9 inches of rainfall annually with predominantly silt loam soil. Summer highs average 87ยฐF, providing good warmth for Tarragon during the growing season.

Douglas County, IL (Zone 5b) Moderate season
186 days
Last Spring Frost April 14
186 growing days
First Fall Frost October 17

Douglas 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 (46 days to spare)
Transplant: Apr 16 🍅 Harvest: Jun 18 – Aug 27
Recommended (50%) ✓ Fits season (46 days to spare)
Transplant: Apr 21 🍅 Harvest: Jun 23 – Sep 1
Safe Start (90%) ✓ Fits season (46 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
0.4″/week
Watering frequency 1-2 times/week
Season total 600 gal / 100 sq ft
Drought risk

Water stress score is 6/10 โ€” consider drought-tolerant varieties and mulching

Tarragon needs ~1,144 GDD — county provides 2,836 GDD Excellent fit

Tarragon Planting Timeline โ€” Douglas County, IL

Tarragon Planting Calendar

Activity When Date Range
Transplant Outdoors April 21 Apr 21 โ€“ May 5
Harvest June 23 Jun 23 โ€“ Sep 1

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

186 days

Growing Tips for Douglas 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 Douglas County, IL?

Douglas County is in Zone 5b with an average last frost of April 14. Plan your Tarragon planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Douglas County, IL?

Douglas County, Illinois is in USDA Hardiness Zone 5b. The average last spring frost is April 14 and first fall frost is October 17.

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Plan Your Garden with Confidence

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