When to plant Tarragon in Johnson County, IL
In Johnson County, Tarragon is a single-season spring crop — there's no second fall window. Plant April 14–April 28 for an 60–90-day harvest, finishing well before the October 21 first frost.
When to Plant Tarragon in Johnson County, IL
Your June gardening checklist
Your garden in Johnson County, Illinois is working on a schedule, even when you're not. Here's where you should be this June.
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Collect tarragon at their peak
This is the payoff month. Bring a basket, bring a friend, and get into the beds.
Looking ahead to July
- First harvests: tarragon
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.
Johnson County, Illinois is in USDA Zone 7a. The average last spring frost is April 7 and the first fall frost is October 21, giving you a growing season of approximately 197 days.
At an elevation of 1,006 feet, Johnson County receives approximately 39.7 inches of rainfall annually with predominantly silt loam soil. Summer highs average 90°F, providing good warmth for Tarragon during the growing season.
Johnson County Soil Profile
Soil Type
Silt Loam
Soil pH
5.9-7.2
Drainage
Well Drained
Tarragon 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 Johnson County
How your county's soil matches Tarragon's growing requirements.
Soil pH
Your soil pH (5.9–7.2) overlaps with Tarragon's range (6.0–7.5), though not a perfect match.
Soil Texture
The silt loam soil in Johnson County is excellent for Tarragon — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is excellent (4.8%) — Tarragon will thrive.
How to Plant Tarragon
Succession Planting Tarragon
Sow every 6.9 weeks. Last sowing by Jul 23 to harvest before frost.
Tarragon 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 | — | 1.9" | 0" | ❄️ Dormant |
| Mar | — | 2.9" | 0" | ❄️ Dormant |
| Apr | 1.7" | 3.6" | 0" | ✅ Rainfall sufficient |
| May | 1.7" | 4.2" | 0" | ✅ Rainfall sufficient |
| Jun | 1.7" | 4.4" | 0" | ✅ Rainfall sufficient |
| Jul | 1.7" | 4.8" | 0" | ✅ Rainfall sufficient |
| Aug | 1.7" | 4.6" | 0" | ✅ Rainfall sufficient |
| Sep | 1.7" | 3.3" | 0" | ✅ Rainfall sufficient |
| Oct | 1.7" | 3.2" | 0" | ✅ Rainfall sufficient |
| Nov | — | 2.9" | 0" | ❄️ Dormant |
| Dec | — | 2.3" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Apr–Oct in Johnson 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 — Johnson County, IL
Tarragon Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 14 | Apr 14 – Apr 28 |
| Harvest | June 16 | Jun 16 – Aug 25 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | Transplant Outdoors |
| May | — |
| June | Harvest |
| July | Harvest |
| August | Harvest |
| September | — |
| 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: acceptable
🗺️ USDA Zone
Zone 7a
📆 Growing Season
197 days in Johnson County
Growing Tips for Tarragon in Johnson County
Direct sow Tarragon outdoors after April 07 in Johnson 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 Johnson County, IL?
Johnson County is in Zone 7a with an average last frost of April 7. Plan your Tarragon planting based on this frost date — see the calendar above for exact timing.
What planting zone is Johnson County, IL?
Johnson County, Illinois is in USDA Hardiness Zone 7a. The average last spring frost is April 7 and first fall frost is October 21.
When should I plant Tarragon in Johnson County, IL?
In Johnson County, IL, plant Tarragon after the last frost (around April 7) and before the first frost (around October 21). Best results when soil holds above 50°F.
What growing zone is Johnson County, IL for Tarragon?
Johnson County sits in USDA Zone 7a. Tarragon grows reliably in zones 4a through 9b, so it's a good fit here.
Can Tarragon grow in Johnson County's climate?
Yes — Tarragon grows well in Johnson County's temperate climate. Johnson County averages a 197-day frost-free season, with last frost around April 7 and first frost around October 21.
Your Johnson County Garden Planner — Free
A 22-page printable planner built for Johnson County (Zone 7a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.