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When to Plant Comfrey in Yolo County, CA

Comfrey is a vigorous perennial herb valued as a dynamic accumulator of nutrients. Its leaves make excellent mulch, compost activator, and liquid fertilizer.

Yolo County, California is in USDA Zone 9a. The average last spring frost is February 9 and the first fall frost is December 3, giving you a growing season of approximately 297 days.

At an elevation of 163 feet, Yolo County receives approximately 27.7 inches of rainfall annually with predominantly loam soil. Summer highs average 95ยฐF, so Comfrey may need afternoon shade and extra watering during peak heat.

Yolo County, CA (Zone 9a) Year-round
297 days
Last Spring Frost February 9
297 growing days
First Fall Frost December 3

Yolo County Soil Profile

Soil Type

Loam

Soil pH

6.7-7.8

Drainage

Well Drained

Plant Planting Risk Windows

Early Start (70% safe) ✓ Fits season (165 days to spare)
Transplant: Feb 1 🍅 Harvest: Apr 5 – Jun 14
Recommended (50%) ✓ Fits season (157 days to spare)
Transplant: Feb 16 🍅 Harvest: Apr 20 – Jun 29
Safe Start (90%) ✓ Fits season (141 days to spare)
Transplant: Mar 20 🍅 Harvest: May 22 – Jul 31

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
0.4″/week
You supply
0.7″/week
Watering frequency 2-3 times/week
Season total 1,940 gal / 100 sq ft
Drought risk

Water stress score is 8/10 โ€” consider drought-tolerant varieties and mulching

Comfrey needs ~1,594 GDD — county provides 6,332 GDD Excellent fit

Comfrey Planting Timeline โ€” Yolo County, CA

Comfrey Planting Calendar

Activity When Date Range
Transplant Outdoors February 16 Feb 16 โ€“ Mar 2
Harvest April 20 Apr 20 โ€“ Jun 29

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

Month-by-Month Timeline

MonthActivities
January โ€”
February Transplant Outdoors
March Transplant Outdoors
April Harvest
May Harvest
June Harvest
July โ€”
August โ€”
September โ€”
October โ€”
November โ€”
December โ€”

Growing Conditions

Sun

Partial Shade (3-6 hours)

Water

Moderate โ€” regular watering

Days to Maturity

60โ€“90 days

Soil pH

6 โ€“ 7

USDA Zone

Zone 9a

Growing Season

297 days

Growing Tips for Yolo County

Plant root cuttings 2 inches deep. Choose Bocking 14 variety to prevent self-seeding. Cut leaves 3-4 times per season for mulch or compost. Avoid planting near pathways as it spreads.

Companion Planting

Good Companions

Level Up Your Garden

Frequently Asked Questions

When should I plant Comfrey in Yolo County, CA?

Yolo County is in Zone 9a with an average last frost of February 9. Plan your Comfrey planting based on this frost date โ€” see the calendar above for exact timing.

What planting zone is Yolo County, CA?

Yolo County, California is in USDA Hardiness Zone 9a. The average last spring frost is February 9 and first fall frost is December 3.

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Plan Your Garden with Confidence

Get our free Garden Planner โ€” designed to help Yolo County gardeners in Zone 9a organize planting dates, track what's growing, and never miss a planting window.

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Free download. Plan your entire garden season in minutes.

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