Symphytum is a genus of flowering plants in the borage family, Boraginaceae, commonly known as comfrey. The genus is native to northern temperate regions of Europe and Asia, with a wide introduced distribution across both continents as well as the Americas.
Taxonomy and Classification
Symphytum was first described by Carl Linnaeus in his 1753 work Species Plantarum. The type species is Symphytum officinale L. The genus belongs to the order Boraginales, family Boraginaceae. There are 27 to 59 recognized species depending on the taxonomic source, with more than 150 species having been cataloged by botanists over time.
Etymology
The name Symphytum derives from the Greek symphytis (meaning "growing together of bones") and phyton (plant), referring to its historical use in traditional medicine for mending bones. The common name "comfrey" comes from the Latin confervere ("to heal" or literally "to boil together").
Description
Symphytum species are perennial herbaceous plants. They have coarse, rough-textured leaves covered in stiff hairs, with large, prominently veined basal leaves. The inflorescences form scorpioid cymes with pendulous, tubular flowers that are typically yellow, blue, or purple. The flowers have a five-lobed corolla and a prominently inflated calyx. The ovary is superior and develops into four obliquely ovoid nutlets. The plants possess fibrous root systems, often with thickened, storage-capable roots. The chromosome base number is x = 8.
Notable Species
- Symphytum officinale L. — common comfrey, the type species
- Symphytum asperum Lepech. — prickly comfrey, rough comfrey
- Symphytum grandiflorum DC. — creeping comfrey
- Symphytum × uplandicum Nyman — Russian comfrey (a hybrid of S. asperum × S. officinale)
- Symphytum tuberosum L. — tuberous comfrey
- Symphytum caucasicum M.Bieb. — Caucasian comfrey
- Symphytum orientale L. — white comfrey
Cultivation and Uses
Some species and hybrids, particularly S. officinale, S. grandiflorum, and S. × uplandicum, are used in gardening and herbal medicine. The Russian comfrey cultivars 'Bocking 4' and 'Bocking 14' were developed during the 1950s by Lawrence D. Hills at the Henry Doubleday Research Association in Bocking, Essex. These cultivars are sterile and are propagated from root cuttings rather than seed.
Comfrey is used in organic gardening as a nutrient-rich mulch and compost activator, and as a source of potassium for plant feed (comfrey tea).
Phytochemistry and Toxicity
Comfrey contains mixed phytochemicals including allantoin, mucilage, saponins, tannins, pyrrolizidine alkaloids, and inulin. Pyrrolizidine alkaloids are responsible for comfrey's liver toxicity when consumed internally. In 2001, the United States Food and Drug Administration (FDA) issued a ban on comfrey products marketed for internal use and required a warning label for those intended for external use. Use of comfrey is discouraged during pregnancy and lactation, in infants, and in people with liver, kidney, or vascular diseases.
Traditional Medicine
Historically, comfrey has been used in folk medicine under names such as knitbone, boneset, and bruisewort, reflecting its traditional application for bone healing and wound treatment. In modern herbalism, comfrey is most commonly used topically. The genus is distinct from Andersonglossum virginianum, known as wild comfrey, which is a different member of the borage family.
