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When to Plant Chervil in San Juan County, CO

Chervil is a delicate herb with a subtle anise-parsley flavor, essential in French cuisine as part of fines herbes. It prefers cool conditions and partial shade.

San Juan County, Colorado is in USDA Zone 4a. The average last spring frost is June 18 and the first fall frost is September 8, giving you a growing season of approximately 82 days.

At an elevation of 7,539 feet, San Juan County receives approximately 20.1 inches of rainfall annually with predominantly loam soil. Summer highs average 82ยฐF, so choose short-season varieties of Chervil to ensure they mature before fall.

San Juan County, CO (Zone 4a) Very short season
82 days
Last Spring Frost June 18
82 growing days
First Fall Frost September 8

San Juan County Soil Profile

Soil Type

Loam

Soil pH

6.3-8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✗ May not fit
Start indoors: Apr 26 Transplant: May 31 🍅 Harvest: Jul 12 – Sep 13
Recommended (50%) ✗ May not fit
Start indoors: May 7 Transplant: Jun 11 🍅 Harvest: Jul 23 – Sep 24
Safe Start (90%) ✗ May not fit
Start indoors: May 18 Transplant: Jun 22 🍅 Harvest: Aug 3 – Oct 5

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.

Plant Water Budget

Plant needs
1.0″/week
Rainfall provides
1.0″/week
You supply
0.3″/week
Watering frequency 1-2 times/week
Season total 237 gal / 100 sq ft
Drought risk

Water stress score is 6/10 โ€” consider drought-tolerant varieties and mulching

Chervil needs ~575 GDD — county provides 943 GDD Excellent fit

Chervil Planting Timeline โ€” San Juan County, CO

Chervil Planting Calendar

Activity When Date Range
Start Indoors May 7 May 7 โ€“ May 21
Transplant Outdoors June 11 Jun 11 โ€“ Jun 25
Direct Sow June 11 Jun 11 โ€“ Jul 2
Fall Sowing June 16 Jun 16 โ€“ Jun 30
Harvest July 23 Jul 23 โ€“ Sep 24

Plant 0.5" deep ยท 8" apart ยท Rows 12" apart

Month-by-Month Timeline

MonthActivities
January โ€”
February โ€”
March โ€”
April โ€”
May Start Indoors
June Transplant Outdoors Direct Sow Fall Sowing
July Direct Sow Harvest
August Harvest
September Harvest
October โ€”
November โ€”
December โ€”

Growing Conditions

Sun

Partial Shade (3-6 hours)

Water

Moderate โ€” regular watering

Days to Maturity

40โ€“60 days

Soil pH

6 โ€“ 7

USDA Zone

Zone 4a

Growing Season

82 days

Growing Tips for San Juan County

Direct sow in early spring or fall as chervil bolts in heat. Provide shade and cool conditions. Harvest outer leaves as needed; use fresh as it loses flavor when dried.

Companion Planting

Good Companions

Level Up Your Garden

Frequently Asked Questions

When should I plant Chervil in San Juan County, CO?

San Juan County is in Zone 4a with an average last frost of June 18. Plan your Chervil planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is San Juan County, CO?

San Juan County, Colorado is in USDA Hardiness Zone 4a. The average last spring frost is June 18 and first fall frost is September 8.

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Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help San Juan County gardeners in Zone 4a organize planting dates, track what's growing, and never miss a planting window.

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Data sources: USDA Plant Hardiness Zone Map (2023), NOAA 30-Year Climate Normals. Frost dates are based on 50% probability averages for San Juan County, CO. Local conditions may vary. Last updated: April 2026.