The issue: Houndstongue

Houndstongue (Cynoglossum officinale) is a poisonous biennial from Eurasia. It is most commonly found in disturbed areas and woodlands, but is becoming more common in pastures, rights-of-way, hiking and riding trails, and even the home landscape.

The oblong houndstongue leaves are rough, quite fuzzy, and up to 12 inches long. The first year they are arranged in a rosette, growing low to the ground. The second growing season the flower bolts, producing seeds in mid-summer

The flower stalks are one to four feet tall, often with a fiddlehead shape. The ¼”, five-petaled flowers are an attractive reddish-burgundy color. The seeds are teardrop-shaped nutlets with Velcro-like barbs, allowing them to cling to animals and hikers.

Houndstongue spreads only by seed. The hitchhiking nutlets drop off and establish plants in new locations—seeds remain viable for two to three years in field conditions.

Houndstongue baled in hay can kill livestock, especially horses and cattle.

Integrated pest management options:

· Prevention: Feed weed-free hay; graze livestock in areas that are free of houndstongue; remove burs from clothing and dog fur and dispose in a plastic bag or burn.

· Mechanical: Mow bolting plants before seed formation to reduce seeds; hand dig plants two inches below the crown; regular cultivation.

· Cultural: Manage lawn and pastures for good grass health.

· Biological: None approved in the U.S. yet; the native police-car moth caterpillar has been known to attack houndstongue; toxic to livestock.

· Chemical: Susceptible to several herbicides—2,4-D, glyphosate, chlorsulfuron, metsulfuron, imazapic, imazapyr—a surfactant will help improve control. Some of these herbicides are not for crop or home landscape situations. Be sure the target weed and crop, or landscape situations are listed on the product label. Always read and follow herbicide label directions.

Combine them:

Combine control techniques for better results.

For more information, contact Ron Patterson, University of Idaho Extension Horticulture/Agriculture Educator in Bonneville County, at 208-529-1390 or