When to Plant Tarragon in DeKalb 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.
DeKalb County, Illinois is in USDA Zone 5a. The average last spring frost is April 22 and the first fall frost is October 16, giving you a growing season of approximately 177 days.
At an elevation of 1,332 feet, DeKalb County receives approximately 34.3 inches of rainfall annually with predominantly silt loam soil. Summer highs average 87°F, providing good warmth for Tarragon during the growing season.
DeKalb County Soil Profile
Soil Type
Silt Loam
Soil pH
6.2-7.2
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 DeKalb County
How your county's soil matches Tarragon's growing requirements.
Soil pH
Your soil pH (6.2–7.2) is within Tarragon's preferred range (6.0–7.5).
Soil Texture
The silt loam soil in DeKalb County is excellent for Tarragon — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Tarragon.
Organic Matter
Organic matter is excellent (5.1%) — Tarragon will thrive.
How to Plant Tarragon
Succession Planting Tarragon
Sow every 6.9 weeks. Last sowing by Jul 18 to harvest before frost.
Plant Water Budget
Water stress score is 6/10 — consider drought-tolerant varieties and mulching
Monthly Watering Guide for Tarragon
Tarragon needs approximately 0.4 inches of water per week (1.7" per month). Here's how your county's rainfall compares month by month.
| Month | Tarragon Needs | Rainfall | You Supplement | Action |
|---|---|---|---|---|
| Jan | — | 1.6" | 0" | ❄️ Dormant |
| Feb | — | 1.4" | 0" | ❄️ Dormant |
| Mar | — | 2.2" | 0" | ❄️ Dormant |
| Apr | 1.7" | 3.1" | 0" | ✅ Rainfall sufficient |
| May | 1.7" | 3.7" | 0" | ✅ Rainfall sufficient |
| Jun | 1.7" | 4.4" | 0" | ✅ Rainfall sufficient |
| Jul | 1.7" | 3.9" | 0" | ✅ Rainfall sufficient |
| Aug | 1.7" | 4.1" | 0" | ✅ Rainfall sufficient |
| Sep | 1.7" | 3.1" | 0" | ✅ Rainfall sufficient |
| Oct | 1.7" | 2.6" | 0" | ✅ Rainfall sufficient |
| Nov | — | 2.6" | 0" | ❄️ Dormant |
| Dec | — | 1.7" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in DeKalb County). Supplement amounts are based on average rainfall — actual needs vary with temperature, soil, and mulching.
Tarragon Heat Requirements (GDD)
What are Growing Degree Days (GDD)?
Growing Degree Days measure the total warmth your plants receive during the growing season. Think of it as a "heat bank" — every day above 50°F deposits warmth that helps your plants grow.
Each plant needs a certain amount of accumulated heat to mature. If your county provides more GDD than the plant needs, it's a great fit. If it's close, you may want to choose faster-maturing varieties or start seeds indoors to get a head start.
Tarragon Planting Timeline — DeKalb County, IL
Tarragon Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 29 | Apr 29 – May 13 |
| Harvest | July 1 | Jul 1 – Sep 9 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Transplant Outdoors |
| May | Transplant Outdoors |
| June | — |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | — |
| November | — |
| December | — |
Growing Conditions
☀️ Sun
Full Sun (6-8+ hours)
💧 Water
0.4"/week · Natural rainfall sufficient
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–7.5 · Your soil: ideal
🗺️ USDA Zone
Zone 5a
📆 Growing Season
177 days in DeKalb County
Growing Tips for Tarragon in DeKalb County
Direct sow Tarragon outdoors after April 22 in DeKalb County when soil has warmed and frost danger has passed.
Common pests for Tarragon in this region include aphids and slugs. Use row covers early in the season and inspect plants weekly.
General growing tips
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
Check more plant combinations with our Companion Planting Checker →
Tarragon in Other Locations
Frequently Asked Questions
When should I plant Tarragon in DeKalb County, IL?
DeKalb County is in Zone 5a with an average last frost of April 22. Plan your Tarragon planting based on this frost date — see the calendar above for exact timing.
What planting zone is DeKalb County, IL?
DeKalb County, Illinois is in USDA Hardiness Zone 5a. The average last spring frost is April 22 and first fall frost is October 16.
Plan Your Garden with Confidence
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