Houndstongue

Houndstongue is a biennial forb in the Boraginaceae (borage) family. It grows from a taproot to form a rosette in its first year of growth; in the second year of growth it produces one to many stems that reach from 1 to 4 feet tall. Leaves are elliptical and have indentations at leaf veins giving them a tongue-like appearance. Lower leaf size varies widely, reaching between 4 and 12 inches or more in length and 1 to 3 inches in width. Lower leaves may have long petioles. Leaves occur alternately on stems and decrease in size up the plant. Upper leaves do not have petioles and clasp the stem. Leaves and stems are covered in soft hairs. Houndstongue flowers from late spring to mid-summer. Flowers are formed in panicles in the axils of upper leaves. Flowers are funnel-shaped, usually ¼ to ⅓ inches across, and contain 5 deep purple or burgundy petals. Each flower produces four seeds or nutlets. Nutlets are ⅓ long, flat, teardrop-shaped, and covered in small barbed hooks.

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Houndstongue produces pyrrolizidine alkaloids in all parts of the plant. These alkaloids are liver toxins to wildlife, livestock, and humans. While livestock may avoid houndstongue when foraging in pasture, dried vegetation is more palatable to livestock but remains toxic increasing the risk of poisoning.

Houndstongue is native to Eurasia and was accidentally introduced to North America in the late-1800s as a contaminant in cereal grain. It spreads solely by seed; hooked barbs on nutlets allow them to be readily dispersed by animals and humans. Houndstongue is frequently found in forests, rangeland and pastures, landscapes, roadsides, and disturbed sites. Dense stands of houndstongue can often be found in areas that wildlife, such as moose, elk or deer, frequent as they rub against trees or rocks which dislodges the nutlets from their fur.

No biological control agents are currently available for release in Teton County; however, initial transect monitoring locations were established in 2023 in anticipation of USDA APHIS PPQ approval of a new agent in the near future.

Because houndstongue has a taproot, it can be readily managed by hand pulling or digging out the root. Tilling or hoeing is also effective for management when the root crown is severed. Controlled grazing is not recommended due to the potential for poisoning. Mowing or chopping will not eradicate stands of houndstongue, but it can be beneficial in preventing seed production. Do not mow while seeds are present.

Larger infestations can be controlled with herbicides. Spring and fall treatments of rosettes are recommended, but treatment of bolting plants can be effective. Flowering plants may be chopped and the remaining rosette and stem treated with herbicide to prevent reflowering. Read the label before using any herbicide. Contact TCWP if you have any questions about application rates or how to use an herbicide.

• Weed Report: Houndstongue from Weed Control in Natural Areas in the Western United States (2013) DiTomaso, Kyser et al. University of California. https://wric.ucdavis.edu/information/natural%20areas/wr_C/Cynoglossum.pdf
• King County Noxious Weed Alert: Houndstongue (2011). King County Noxious Weed Control Program, King County, Washington. https://your.kingcounty.gov/dnrp/library/water-and-land/weeds/Brochures/Houndstongue_factsheet.pdf
• Houndstongue: Identification and Control STOP THE SPREAD (2008). Lym, R.G. North Dakota State University. Department of Plant Sciences. https://www.ag.ndsu.edu/publicationS/crops/houndstongue-cynoglossum-officinale-l-identification-and-control-stop-the-spread
• Houndstongue. Washington State Noxious Weed Control Board. https://www.nwcb.wa.gov/weeds/houndstongue