When to Plant Tarragon in San Juan County, WA
May to-do list for San Juan County, Washington
We've pulled the most time-sensitive tasks for San Juan County, Washington this May and put them front and centre. Tackle them in order.
A few tasks this May that'll pay off in June
- 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.
San Juan County, Washington is in USDA Zone 9a. The average last spring frost is March 26 and the first fall frost is November 3, giving you a growing season of approximately 222 days.
At an elevation of 371 feet, San Juan County receives approximately 40.9 inches of rainfall annually with predominantly silt loam soil. Summer highs average 82°F, so choose short-season varieties of Tarragon to ensure they mature before fall.
San Juan County Soil Profile
Soil Type
Silt Loam
Soil pH
5.4-6.4
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 San Juan County
How your county's soil matches Tarragon's growing requirements.
Soil pH
Your soil pH (5.4–6.4) is more acidic than Tarragon prefers (6.0–7.5). Add garden lime to raise pH.
Soil Texture
The silt loam soil in San Juan 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 (4.8%) — Tarragon will thrive.
How to Plant Tarragon
Succession Planting Tarragon
Sow every 6.9 weeks. Last sowing by Aug 05 to harvest before frost.
Plant Water Budget
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 | — | 5.7" | 0" | ❄️ Dormant |
| Feb | — | 4.7" | 0" | ❄️ Dormant |
| Mar | 1.7" | 4.1" | 0" | ✅ Rainfall sufficient |
| Apr | 1.7" | 2.6" | 0" | ✅ Rainfall sufficient |
| May | 1.7" | 2.6" | 0" | ✅ Rainfall sufficient |
| Jun | 1.7" | 1.5" | 0.2" | 💧 Light watering |
| Jul | 1.7" | 0.6" | 1.1" | 🚿 Regular watering |
| Aug | 1.7" | 0.8" | 0.9" | 🚿 Regular watering |
| Sep | 1.7" | 1.8" | 0" | ✅ Rainfall sufficient |
| Oct | 1.7" | 3.4" | 0" | ✅ Rainfall sufficient |
| Nov | 1.7" | 6.4" | 0" | ✅ Rainfall sufficient |
| Dec | — | 6.6" | 0" | ❄️ Dormant |
Water needs are for active growing months only (Mar–Nov in San Juan 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 — San Juan County, WA
Tarragon Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | April 2 | Apr 2 – Apr 16 |
| Harvest | June 4 | Jun 4 – Aug 13 |
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: too_acidic
🗺️ USDA Zone
Zone 9a
📆 Growing Season
222 days in San Juan County
Growing Tips for Tarragon in San Juan County
Direct sow Tarragon outdoors after March 26 in San Juan 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 San Juan County, WA?
San Juan County is in Zone 9a with an average last frost of March 26. Plan your Tarragon planting based on this frost date — see the calendar above for exact timing.
What planting zone is San Juan County, WA?
San Juan County, Washington is in USDA Hardiness Zone 9a. The average last spring frost is March 26 and first fall frost is November 3.
Your San Juan County Garden Planner — Free
A 24-page printable planner built for San Juan County (Zone 9a). Planting dates, a month-by-month schedule, harvest log, seed inventory, and succession charts — all dialed in for your exact growing season.