When to Plant Comfrey in Mercer County, PA
Comfrey is a vigorous perennial herb valued as a dynamic accumulator of nutrients. Its leaves make excellent mulch, compost activator, and liquid fertilizer.
Mercer County, Pennsylvania is in USDA Zone 5b. The average last spring frost is May 6 and the first fall frost is October 17, giving you a growing season of approximately 164 days.
At an elevation of 63 feet, Mercer County receives approximately 43.3 inches of rainfall annually with predominantly silt loam soil. Summer highs average 84°F, so choose short-season varieties of Comfrey to ensure they mature before fall.
Mercer County Soil Profile
Soil Type
Silt Loam
Soil pH
5.1-6.5
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 Mercer County
How your county's soil matches Comfrey's growing requirements.
Soil pH
Your soil pH (5.1–6.5) is more acidic than Comfrey prefers (6.0–7.0). Add garden lime to raise pH.
Soil Texture
The silt loam soil in Mercer County is excellent for Comfrey — good drainage, moisture retention, and nutrient holding capacity.
Organic Matter
Organic matter is moderate (3.5%). Annual compost additions will help Comfrey.
How to Plant Comfrey
Succession Planting Comfrey
Sow every 6.9 weeks. Last sowing by Jul 19 to harvest before frost.
Plant Water Budget
Comfrey Planting Timeline — Mercer County, PA
Comfrey Planting Calendar
| Activity | When | Date Range |
|---|---|---|
| Transplant Outdoors | May 13 | May 13 – May 27 |
| Harvest | July 15 | Jul 15 – Sep 23 |
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
Partial Shade (3-6 hours)
💧 Water
1"/week · Natural rainfall sufficient
📅 Days to Maturity
60–90 days
🧪 Soil pH
Needs 6–7 · Your soil: too_acidic
🗺️ USDA Zone
Zone 5b
📆 Growing Season
164 days in Mercer County
Growing Tips for Comfrey in Mercer County
Direct sow Comfrey outdoors after May 06 in Mercer County when soil has warmed and frost danger has passed.
General growing tips
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
Comfrey in Other Locations
Frequently Asked Questions
When should I plant Comfrey in Mercer County, PA?
Mercer County is in Zone 5b with an average last frost of May 6. Plan your Comfrey planting based on this frost date — see the calendar above for exact timing.
What planting zone is Mercer County, PA?
Mercer County, Pennsylvania is in USDA Hardiness Zone 5b. The average last spring frost is May 6 and first fall frost is October 17.
Plan Your Garden with Confidence
Get our free Garden Planner — designed to help Mercer County gardeners in Zone 5b organize planting dates, track what's growing, and never miss a planting window.
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