Comfrey is a perennial medicinal herb, long valued for its traditional uses. It's hardy across USDA zones 4 through 8 and stands up to deer. Its summer flowers are a real draw for honeybees and native bees.
Comfrey — the short answer
Comfrey: grown in zones 4–8, part sun, pH 5.5–8, about 85 days to maturity.
- USDA zones
- 4–8
- Manual horticultural correction (source not retained); NC State Extension and Missouri Botanical Garden, with the remaining rows from other published sources or Growable Ground compilation
- Soil pH
- 5.5–8
- Growable Ground Plant Database
- Sun
- Part Sun
- Growable Ground Plant Database
- Days to Maturity
- 85 days
- USDA-NRCS
- Frost-kill temperature
- -22°F
- Growable Ground Plant Database
Plant data: Growable Ground Plant Database, compiled from FAO ECOCROP, USDA PLANTS and university Extension sources — each tile names its own row's source, because per-field provenance varies.
Score Comfrey on your exact land.
Zone averages can't see the slope, soil, frost, and sun that decide whether comfrey actually takes — and those shift from one yard to the next. Enter your address and we'll score comfrey against your land's real conditions.
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
No card required · your full report in seconds
What Comfrey is
Comfrey grows as a perennial and reaches around three feet at maturity. It blooms purple in summer. It's also deer-resistant.
How to grow Comfrey
Comfrey grows in USDA zones 4 through 8 and is ready to harvest about 85 days after planting. Comfrey does best in part sun — at least 4 hours of direct sun a day — and soil from pH 5.5 to 8, on well-drained ground. It needs around 1,800 growing degree days to mature and a growing season of at least 90 frost-free days, which is why climate matters as much as soil.
USDA Zones
4-8
USDA PHZM 2023
Soil pH
5.5 - 8
Growable Ground Plant Database
Sun
Part Sun
Growable Ground plant catalog
Drainage
well (dry spells)
Growable Ground plant catalog
Frost Kill Temperature
-22°F
Where cold starts killing growing tissue. Not a winter-survival floor — a dormant perennial takes far colder, which its hardiness zone answers.
Growable Ground Plant Database
Days to Maturity
85 days
Comfrey; perennial; propagated by root division (not seed). Cut for mulch / chop-and-drop.
USDA-NRCS
GDD Required
1800+
Growing degree-days of accumulated warmth it needs to mature — humid summers reach this faster than cool coastal ones.
Growable Ground plant catalog
Mature Height
3 ft
Growable Ground plant catalog
Frost-Free Days
90+
The frost-free stretch it needs start to finish — short-season areas may need an indoor head start.
Growable Ground plant catalog
Start the season right
Plant comfrey in part sun with at least 4 hours of direct sun. It grows in the cool halves of the year, so sow it in spring or late summer rather than waiting for midsummer heat.
Match the soil
Comfrey prefers pH 5.5 to 8 (Growable Ground Plant Database). A quick soil test from your local Extension lab tells you whether to add lime or sulfur to land in band.
Water steadily
Keep the root zone evenly moist through establishment. A 2–3 inch mulch layer holds moisture without waterlogging.
Harvest at its peak
Harvest the part you grow comfrey for — flower, leaf, or root — at its seasonal peak.
Where Comfrey thrives
Comfrey is hardy across USDA zones 4 through 8. Zone is only the starting point, though: the soil pH, drainage, and frost dates on your specific land decide how well it actually does.
A USDA zone is a 10°F band of average annual extreme winter minimum, so zones 4–8 spans average winter lows from -30°F to 20°F (USDA PHZM 2023). Across the 50 states and DC, that band covers 25 outright and splits 26 more down the middle — and which side of that line your land sits on changes the answer.
Zones 4–8·Where Comfrey growsOpen map →
Where Comfrey stands, state by state
Comfrey is rated for zones 4–8 — a cold floor USDA puts at -30 to -20°F. Across the 50 states and DC, 25 sit fully inside that band, the line runs through 26 more, and 0 sit outside it — and inside every split state, the same line runs on at county grain.
Fully inside zones 4–8
25 states
3 of 25 shown
State zone extents: USDA Plant Hardiness Zone Map (PHZM) 2023. A zone is a 10°F band of average annual extreme minimum temperature, so a state that splits the band contains the boundary — its own page draws the county line, and a parcel report resolves which side your land sits on.
What grows around Comfrey
Growing guides for comfrey
In rotation planning, comfrey counts as a Other — beds recover best when other crops don’t follow each other in the same spot year over year. (Growable Ground derivation — crop-rotation group from botanical family)
Good to know
One caution for pet owners — comfrey is toxic to dogs and cats (moderate severity). Keep it out of reach, and call ASPCA Animal Poison Control at (888) 426-4435 in an emergency. (Source: ASPCA.)
Comfrey is a standout pollinator plant — high value to bees and other pollinators. (Source: Xerces Society.)
Before you harvest comfrey, know your soil
Anything you grow to eat takes up what's in the ground it grows in, so it's worth knowing what's documented near you before you plant comfrey for food. Our free screen reads 9 federal source types across roughly 1.8M indexed sites and shows which sit near your address and which way they drain. It's a screening estimate from public records and proximity — not a soil test — so a nearby record means a soil test is worth it, not that your soil is unsafe.
Your land is one point inside Comfrey's range
This page resolves to the species. Your state page draws the county line, and a report reads the parcel — the soil pH, drainage, sun, and frost dates on your exact ground, which no species average can see.
See if Comfrey will thrive on your land
Zone averages are a start. Your exact soil pH, drainage, sun exposure, and frost dates shape whether comfrey actually takes — we score it against the real conditions at your address.
Three things about your exact spot that zone averages miss:
We read public map data for this spot — soil, climate, flood, and parcel records. How we handle your address.
25+ data sources analyzed in seconds
How we know this about Comfrey
The figures above are cited per row, not per site: the pH band names this plant’s own source column, the three temperature figures each carry their own, and days-to-maturity cites the publication that actually lists it. All of it comes from the Growable Ground Plant Database — a compilation over FAO ECOCROP, USDA PLANTS, and university Extension sources, published openly with per-field provenance.
Grounded inUSDA PLANTS Database•USDA PHZM•ASPCA
Frequently asked questions
Can I grow Comfrey in my zone?
Comfrey grows in USDA hardiness zones 4 through 8 (USDA PHZM 2023). Zone is one factor — soil pH, drainage, and frost dates on your specific parcel also shape whether it takes.
How long does Comfrey take to grow?
Comfrey is ready to harvest about 85 days after planting (USDA-NRCS). Your local frost dates and soil temperature move that window earlier or later.
When should you plant Comfrey?
Comfrey is a cool-season crop, so it goes in during the cool halves of the year — early spring, and again in late summer for a fall planting — rather than at the height of summer heat. Your local frost dates set the exact window — a Growable Ground report reads them for your address.
How much sun does Comfrey need?
Comfrey does well in partial sun — around 4 hours of direct sun, and it takes some afternoon shade in stride. That flexibility makes it a good match for a bed the house or a nearby tree shades for part of the day. A Growable Ground report maps how the sun actually falls on your land, hour by hour, so you can set it where the light lines up.
What soil does Comfrey need?
Comfrey prefers soil pH 5.5 to 8, on well-drained ground (Growable Ground Plant Database). Your report scores your parcel's actual soil against that using USDA SSURGO data.
Does Comfrey attract pollinators?
Yes — comfrey's flowers are a strong nectar and pollen source for honeybees and native bees. (Source: Xerces Society.)
Is Comfrey safe for pets?
Comfrey is toxic to pets (dogs,cats) with moderate severity. Keep it out of reach, and call ASPCA Animal Poison Control at (888) 426-4435 in an emergency. (Source: ASPCA.)