Cynoglossum officinale L.

Houndstongue

Identification

Houndstongue

Cynoglossum officinale L.

Life cycle: Biennial
Height: 1 to 4 ft

Houndstongue is a biennial that forms a rosette the first year and bolts and flowers the second. The leaves are oblong, very hairy and rough. Plants grow 1 to 4 feet tall and flower in midsummer. Flowers are small, red to burgundy and arranged in clusters.

Each flower produces three or four nutlets with a very hard coat, covered with barbs. The barbs cling to clothing, machinery and animals, which lets the plant spread long distances.

Plants are generally found in wooded areas or in pastures near trees and shrubs. Nutlets on sheep can reduce the value of wool and can irritate animals if they become embedded near the eye. Houndstongue contains alkaloids that are especially toxic to cattle and horses. Animals rarely graze green plants but will eat dried plants in hay.

Control

Controlling houndstongue

Best timing: First year rosettes are easy to control with 2,4-D in late May to mid June. Second year plants are much less susceptible.
Mowing and pulling: Buy only certified weed seed free hay, and remove new infestations before they spread.
Herbicide: Metsulfuron (Escort) is very effective and can be applied all season. Imazapic (Plateau) works at high rates but may injure cool season grasses.
Biological control: None is approved for release in the United States.

Always follow the product label, and check rates in the North Dakota Weed Control Guide from NDSU. Your county weed control officer can tell you what fits your land. Source: NDSU Extension W1411 (December 2025).

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