Ohio Perennial and Biennial Weed Guide

Family:

Borage Family (Boraginaceae)

Other Names:

asses-ears, backwort, blackwort, boneset, bruisewort, consound, gumplant, healing herb, knitback, knitbone, slippery-root.

Origin and Distribution:

A European species, common comfrey was introduced into North America as a medicinal herb. In the U.S., it is presently scattered throughout the eastern half of the country. In Ohio, there is a greater tendency for the plant to occur as a weed in the north. This introduced herb is highly adaptable and has become a naturalized weed in ditches, meadows, abandoned gardens, and waste places. Common comfrey prefers rich soils containing lime and moist, shady sites.

Plant Description:

Common comfrey is a perennial herb with lower leaves that are bristly, up to 12 inches long, and attached to winged leaf stalks (petioles) that emerge from the base of the plant. Smaller leaves that are also bristly but lack petioles are borne on 2- to 3-foot tall flowering stems. Flowers are bell shaped and either yellow or blue. They form in distinctive curled clusters having an appearance similar to that of a scorpion's tail. Reproduction is by way of seeds. Also, new plants can be propagated by dividing the roots of established plants.

• Root System:

  Roots are branched, spindle-shaped, less than 1 inch in diameter, and more than 1 foot long. The outside is covered with black bark and the inside is white, fleshy, and juicy.

• Stems:

  Stems are 2 to 3 feet tall, erect, angular, hollow, branched, and terminate in a cluster of flowers. Stems are covered with rough hairs and feel prickly.

• Leaves:

  Both sides of leaves are covered with rough hairs. The undersides of leaves have conspicuous veins. Lower leaves emerging from the base of the plant are 3 to 12 inches long and have smooth edges. Their shape is such that they appear to narrow gradually at the base into long, succulent, winged leaf stalks (petioles). Leaves located on stems are alternate, lance-shaped, and smaller than basal leaves. Instead of attaching to the stem by way of petioles, they form wings that extend down around the stem.

• Flowers:

  Flowers are 1/2-inch-long, bell shaped, and borne in 1-sided, curled clusters that resemble a scorpion's tail. Located nearest the stem is the most fully-expanded blossom and immature buds can usually be found at the extremity of the cluster. Flower color depends on variety and can be either white, creamy yellow, or pink fading to blue.

• Fruits and Seeds:

  As flowers mature, 4 nutlike fruits develop that are brownish-black with a nearly smooth, somewhat shiny surface.

Similar Species:

Common comfrey leaves appear similar to foxglove (Digitalis purpurea) leaves except their surface is covered by stiff hairs and their shape is more lanceolate than those of foxglove. Also, common comfrey flowers are about 1/2 inch long while foxglove flowers are large and showy.

Biology:

Common comfrey blooms between May and August.

Toxicity:

All parts of common comfrey contain toxic alkaloids. Roots appear to be more toxic than stems and leaves. Repeated ingestion can lead to serious liver damage and death. Children are more susceptible than adults. Animals usually avoid mature leaves due to the coarse hairs and unpleasant taste.

Facts and Folklore:

• Common comfrey has been a popular medicinal herb and its roots and flowers were ground, beaten, boiled, and used to treat numerous ailments. Common comfrey was given internally to stop bleeding, encourage mending of broken bones, and relieve muscle pain. Roots were ground and applied to open wounds to encourage healing.

• In Europe, common comfrey was used as a forage plant.