Houndstongue (Cynoglossum officinale L.) is a non-native, poisonous weed which infests pastures, hay fields and disturbed areas throughout North America. It was accidentally introduced to North America from Eurasia as a cereal contaminant prior to the 1900s. Houndstongue displaces native rangeland vegetation by capturing soil resources with its deep, well-anchored taproot. In Montana, houndstongue currently infests an estimated 36,000 acres. Montana's houndstongue management goals are to control existing infestations and to prevent or minimize the further spread of this weed.

Growth Habit: Houndstongue, a member of the Boraginaceae (Borage) family, is a biennial or short-lived perennial. Houndstongue develops from seedling to rosette within the first year of growth (Figure 1). Leaves are oblong with numerous soft white hairs on both surfaces, possess prominent veins and are said to look like a hound's tongue. During the second year of growth, plants produce a flowering stalk 8 to 30 inches tall (Figure 2). Flowers form in mid-June and range in color from dull red to burgundy. Each flower develops seed clusters containing 3-4 fruits or nutlets roughly 1/4 inch long. Fruits are flat, teardrop-shaped and possess a hard spiny husk with barbs (Figure 3). In Montana, houndstongue seed production ranges from 300-675 seeds per plant each year.

Spread: Houndstongue seeds are dispersed to disturbed pastures, meadows, waste places, roadsides, riparian areas and forested land when they become entangled in hair, wool or clothing. Although dispersal occurs slowly over time, colonization of disturbed sites can take place very quickly. Seeds are covered in a spiny husk and possess a protruding barb which enables the seed to adhere to wildlife and livestock. Recent research suggests that cattle are major disperses of houndstongue, picking up about 65 percent of burr stalks in grazed paddocks. Seeds may over winter within the top 1 centimeter of soil or remain attached to an adult plant. Houndstongue seeds are viable for two to three years and do not form large or persistent seed banks in the soil. Germination generally requires some form of scarification or softening of the seed coat.

Toxic: Common names such as sheep's lice, dog's bur, beggar's lice, woolmat and glovewort suggest the problematic nature of houndstongue nutlets. When nutlets become imbedded in the wool or hair of livestock, they may create marketing problems for ranchers because of the extra time and money required for their removal. They can also become lodged in the eyelashes of livestock causing potentially severe eye damage. After nutlets are removed from clothing or animals, they should be burned in hot fire. Another concern for ranchers is the threat of livestock poisoning from houndstongue although, in most cases, the fresh plant is considered unpalatable by livestock and is generally avoided. Houndstongue contains pyrroli?zidine alkaloids or PAs which may cause liver damage or failure in horses and cattle but not sheep. Poisoning can potentially occur when houndstongue is cut and dried with harvested hay or when animals are confined to a small area lacking desirable forage. Poisoning occurs when animals consume sufficient quantities of plant material with high pyrrolizidine alkaloid concentrations. PA levels are generally highest in immature plants (1.5 to 2.0 percent dry weight) and decrease with maturation. The acute or chronic nature of poisoning depends on the PA concentration, amount eaten and rate of ingestion. Some clinical signs of PA poisoning for cattle include: