German Comfrey Plants

Name Clarifications

• The species Symphytum officinale is also commonly referred to as the common comfrey. In the past, plant taxonomists included a regional variety of it, bohemicum, and later gave it a similar species designation of Symphytum bohemicum. Today, botanists regard these names as synonyms and refer to the same plant -- Symphytum officinale -- according to the Royal Botanic Garden in Edinburgh, Scotland. The species Symphytum tuberosum was historically dubbed German tuberous comfrey, although today it's most commonly referred to simply as tuberous comfrey.

Features

• Growing from rhizome roots, both species of German comfrey plants produce hairy, crinkle-veined, pointed oval green leaves on hairy stems. Leaves may measure up to 10 inches long. Symphytum officinale matures 3 to 5 feet tall and 6 feet wide. From late spring into summer, it bears forked clusters of violet, pink or creamy yellow flowers. Symphytum tuberosum grows much more prostrate, only 16 to 24 inches tall but spreading 3 feet wide. In early summer, it produces pale yellow flowers in loose, spiraled clusters. Digging up a plant reveals plump, tuberlike rhizomes compared to Symphytum officinale.

Growing German Comfreys

• Comfrey plants grow quickly and spread in landscapes, often becoming rampant groundcovers in woodland or shade garden settings. They prosper in moist soils that have any amount of fertility, and they tolerate full sun to partial shade. Subfreezing temperatures kill plants back to their roots, but they resprout in spring. Once in a garden, plants spread by roots or scattering of seeds. Digging up roots can lead to problems, as any root fragments left in the soil may sprout into new plants. Symphytum officinale is a hardier plant, appropriate for U.S. Department of Agriculture plant hardiness zones 3b through 9a. Symphytum tuberosum grows only in USDA zones 5 through 9.

Caveats

• All comfrey plant species contain poisonous compounds called pyrrolizidine alkaloids, most concentrated in roots. These toxins can cause severe liver damage or death. Symphytum officinale was once used medicinally to treat stomach ailments, but since 2001, the U.S. Food and Drug Administration has prohibited any oral products containing comfrey, particularly of species Symphytum officinale. The United Kingdom, Australia, Canada and Germany have also banned sale of oral products containing comfrey. Ointments and creams for topical skin use are still available.