Coarse-leaved perennial with deep taproot. A workhorse of permaculture gardens for compost activator, mulch, and chop-and-drop fertility.
Hardiness ratings
| System | Rating | Temperature range | How to read it |
|---|---|---|---|
| USDA hardiness zone | Zone 3–9 | −40 °C to −1.1 °C | Plant tolerates down to this zone |
| RHS hardiness rating | H7 | down to −20 °C | Plant needs at least this level of cold tolerance |
| Canadian plant hardiness zone | Zone 3–9 | −34 °C and warmer | Plant tolerates down to this zone |
| Australian (ANBG) zone | Zone 1–5 | −15 °C to 10 °C | Plant tolerates down to this zone |
About Comfrey
Comfrey is grown less for itself than for what it does to soil. Its roots go down a long way, drawing up nutrients that shallower plants cannot reach, and the leaves break down quickly, which is why gardeners cut them for mulch and steeped liquid feed. The Bocking 14 cultivar is widely preferred for this because it is sterile and will not seed itself around, though it still spreads from root fragments and is very difficult to remove once established. Historically it was used to treat sprains and fractures, giving it the old country name knitbone.
Growing notes
- Choose Bocking 14, a sterile cultivar — the fertile species spreads aggressively from seed and root fragments
- Wilted leaves are an excellent potassium-rich mulch around tomatoes and fruit trees
- Always consult a qualified medical or herbal practitioner before medicinal use.
Pet caution: Comfrey is listed as potentially harmful to cats and/or dogs. Keep pets from grazing on it, and contact a vet if you suspect your animal has eaten some.
Categories
Related plants
Cross-check Comfrey against your zones