When to Plant Tarragon in Jefferson County, ID
May in the garden — Jefferson County, Idaho
May rewards gardeners who work with the weather, not against it. Here's how to stay in step this month in Jefferson County, Idaho.
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Move tarragon into the garden
Pick a cloudy afternoon or evening to plant. Less transplant shock, and your seedlings will barely blink.
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.
Jefferson County, Idaho is in USDA Zone 5a. The average last spring frost is May 22 and the first fall frost is September 21, giving you a growing season of approximately 122 days.
At an elevation of 5,094 feet, Jefferson County receives approximately 18 inches of rainfall annually with predominantly loam soil. Summer highs average 87°F, providing good warmth for Tarragon during the growing season. With low rainfall, drip irrigation is essential for growing Tarragon successfully. Mulch heavily to conserve soil moisture.
Jefferson County Soil Profile
Soil Type
Loam
Soil pH
6.3-7.8
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 Jefferson County
How your county's soil matches Tarragon's growing requirements.
Soil pH
Your soil pH (6.3–7.8) overlaps with Tarragon's range (6.0–7.5), though not a perfect match.
Soil Texture
The loam soil in Jefferson County is excellent for Tarragon — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (2.4%). Annual compost additions will help Tarragon.
How to Plant Tarragon
Succession Planting Tarragon
Sow every 6.9 weeks. Last sowing by Jun 23 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 | — | 1.1" | 0" | ❄️ Dormant |
| Feb | — | 1.2" | 0" | ❄️ Dormant |
| Mar | — | 1.4" | 0" | ❄️ Dormant |
| Apr | — | 2" | 0" | ❄️ Dormant |
| May | 1.7" | 1.9" | 0" | ✅ Rainfall sufficient |
| Jun | 1.7" | 1.4" | 0.3" | 💧 Light watering |
| Jul | 1.7" | 1.4" | 0.3" | 💧 Light watering |
| Aug | 1.7" | 2" | 0" | ✅ Rainfall sufficient |
| Sep | 1.7" | 1.6" | 0.1" | 💧 Light watering |
| Oct | — | 1.6" | 0" | ❄️ Dormant |
| Nov | — | 1.3" | 0" | ❄️ Dormant |
| Dec | — | 1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Sep in Jefferson 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 — Jefferson County, ID
Tarragon Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 29 | May 29 – Jun 12 |
| Harvest | July 31 | Jul 31 – Oct 9 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| May | Transplant Outdoors |
| June | Transplant Outdoors |
| July | Harvest |
| August | Harvest |
| September | Harvest |
| October | Harvest |
| 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 5a
📆 Growing Season
122 days in Jefferson County
Growing Tips for Tarragon in Jefferson County
Direct sow Tarragon outdoors after May 22 in Jefferson 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 Jefferson County, ID?
Jefferson County is in Zone 5a with an average last frost of May 22. Plan your Tarragon planting based on this frost date — see the calendar above for exact timing.
What planting zone is Jefferson County, ID?
Jefferson County, Idaho is in USDA Hardiness Zone 5a. The average last spring frost is May 22 and first fall frost is September 21.
Your Jefferson County Garden Planner — Free
A 24-page printable planner built for Jefferson County (Zone 5a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.