When to Plant Tarragon in Washington County, ID
This month in Washington County, Idaho
A quick May briefing for Washington County, Idaho gardeners — what's urgent, what's next, and what can wait.
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Set out tarragon seedlings
Your last frost (May 9) has passed. These warm-season crops can handle outdoor soil now.
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.
Washington County, Idaho is in USDA Zone 7a. The average last spring frost is May 9 and the first fall frost is October 1, giving you a growing season of approximately 145 days.
At an elevation of 4,048 feet, Washington County receives approximately 17.9 inches of rainfall annually with predominantly loam soil. Summer highs average 85°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.
Washington County Soil Profile
Soil Type
Loam
Soil pH
6.2-7.8
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 Washington County
How your county's soil matches Tarragon's growing requirements.
Soil pH
Your soil pH (6.2–7.8) overlaps with Tarragon's range (6.0–7.5), though not a perfect match.
Soil Texture
The loam soil in Washington County is excellent for Tarragon — good drainage, moisture retention, and nutrient holding capacity.
Drainage
Drainage is adequate for Tarragon.
Organic Matter
Organic matter is moderate (2.5%). Annual compost additions will help Tarragon.
How to Plant Tarragon
Succession Planting Tarragon
Sow every 6.9 weeks. Last sowing by Jul 03 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 | — | 1.9" | 0" | ❄️ Dormant |
| Apr | — | 1.7" | 0" | ❄️ Dormant |
| May | 1.7" | 2" | 0" | ✅ Rainfall sufficient |
| Jun | 1.7" | 1.2" | 0.5" | 💧 Light watering |
| Jul | 1.7" | 1.6" | 0.1" | 💧 Light watering |
| Aug | 1.7" | 1.7" | 0" | ✅ Rainfall sufficient |
| Sep | 1.7" | 1.5" | 0.2" | 💧 Light watering |
| Oct | 1.7" | 1.5" | 0.2" | 💧 Light watering |
| Nov | — | 1.4" | 0" | ❄️ Dormant |
| Dec | — | 1" | 0" | ❄️ Dormant |
Water needs are for active growing months only (May–Oct in Washington 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 — Washington County, ID
Tarragon Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 16 | May 16 – May 30 |
| Harvest | July 18 | Jul 18 – Sep 26 |
Plant 0.5" deep · 8" apart · Rows 12" apart
Month-by-Month Timeline
| Month | Activities |
|---|---|
| January | — |
| February | — |
| March | — |
| April | — |
| 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 · Only during dry spells
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–7.5 · Your soil: acceptable
🗺️ USDA Zone
Zone 7a
📆 Growing Season
145 days in Washington County
Growing Tips for Tarragon in Washington County
Direct sow Tarragon outdoors after May 09 in Washington 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 Washington County, ID?
Washington County is in Zone 7a with an average last frost of May 9. Plan your Tarragon planting based on this frost date — see the calendar above for exact timing.
What planting zone is Washington County, ID?
Washington County, Idaho is in USDA Hardiness Zone 7a. The average last spring frost is May 9 and first fall frost is October 1.
Your Washington County Garden Planner — Free
A 24-page printable planner built for Washington 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.