Houndstongue (Cynoglossum officinale L.)
Houndstongue is a biennial forb that develops from a taproot. In its first year, it forms a leafy basal rosette. During the second year, it produces one to several upright flowering stems that typically grow 1–4 feet tall.
The plant is named for its distinctive leaves, which are long, elliptical, and resemble a dog’s tongue. Leaves are arranged alternately along the stems and decrease in size toward the top of the plant. Lower leaves can range from 4–12 inches (or more) in length and 1–3 inches in width, often with long petioles. Upper leaves lack petioles and clasp the stem. Both leaves and stems are covered in soft hairs, giving them a rough texture.
Flowering occurs from late spring through mid-summer. Flowers are borne in branched clusters (panicles) in the upper leaf axils. Each flower is funnel-shaped, about ¼–â…“ inch across, with five deep purple to burgundy petals. Small, pale “crystals” or scales are visible in the center of the flower.
Each flower produces four seeds (nutlets). The nutlets are flat, teardrop-shaped, and covered with numerous small barbed hooks that cling to clothing, fur, and equipment—an effective dispersal mechanism.
Houndstongue contains pyrrolizidine alkaloids in all parts of the plant. These compounds are toxic to livestock, wildlife, and humans, causing liver damage. While grazing animals may avoid fresh plants, dried houndstongue in hay remains toxic and may increase the risk of poisoning.
​
toxic to livestock, wildlife, and humans
​
​
Quick ID
Life Cycle:
• Biennial
• Basal rosette first year
• Flowering stems second year
• Taproot
Height:
• 1–4 feet tall
Leaves:
• Long, tongue-shaped
• Alternate arrangement
• Lower leaves are large with petioles
• Upper leaves clasp the stem
• Soft, hairy texture
Flowers (Late Spring–Mid-Summer):
• Deep purple to burgundy
• 5 petals• ¼–â…“ inch wide
• Small pale scales in the center
Seeds:
• Four nutlets per flower
• Flat, teardrop-shaped
• Covered in barbed hooks
Management Options
Because houndstongue grows from a taproot, it can often be effectively controlled by hand pulling or digging, provided the entire root is removed. Tilling or hoeing may also be effective if the root crown is severed below the soil surface. Controlled grazing is not recommended due to the risk of poisoning. Mowing or chopping will not eliminate established stands, but can help reduce seed production if completed before seeds mature. Do not mow once seeds are present.
Large infestations may require herbicide treatment. Applications targeting rosettes in spring or fall are most effective, although treatments applied to bolting plants can also provide control. Flowering plants may be cut, and the remaining rosettes or regrowth treated with herbicide to prevent reflowering. Always read and follow the herbicide label before use. Contact Sublette County Weed & Pest for guidance on product selection, rates, and application timing.
