Some of the Most Common Noxious Weeds in Montana
Photo: Joseph M. DiTomaso, University of California-Davis, Bugwood.org
Dalmation toadflax is a short-lived, herbaceous perennial in the figwort family that grows up to four feet tall. Stems are somewhat woody at the base and often branch in the upper portion. Leaves and stems are waxy, leaves are heart-shaped and one to three inches long with clasping bases. Flowers are bright yellow with orange markings. Dalmation toadflax infests 174,000 acres in Montana. Though common in some areas, others remain uninfested. It is critical to fish and wildlife habitat to control this noxious weed.
Photographer: John Cardina, Ohio State University, Bugwood.org
Spotted knapweed is an herbaceous biennial or perennial plant that invades open areas throughout most of the U.S. Its name is derived from the black margins of the flower bract tips which give the flower heads a spotted look. A basal rosette of deeply lobed leaves is produced the first year. Rosette leaves may grow to eight inches long. Flowering stems grow up to four feet in height and branch. Flowering occurs in the mid to late summer. Flowers are purple to pink on small flower heads. Spotted knapweed infests 2.7 million acres in Montana and is common in many areas though there are uninfested areas. It is critical to fish and wildlife habitat to control this noxious weed.
Photo: USDA APHIS PPQ Archive, Bugwood.org
Leafy spurge is an erect, perennial, herbaceous plant that grows from two to three feet tall. Leaves are oval, smooth and one to four inches long. The plant produces a milky sap if the stem is broken or a leaf is removed. The stem is smooth and bluish-green. Flowering occurs in the late summer or summer when yellow flowers develop in clusters at the apex of the plant. Large infestations give the landscape a yellowish tinge due to the yellow bracts. This plant can completely overtake large areas of land and displace native vegetation. It infests 797,000 acres in Montana, though many areas remain uninfested. It is critical to fish and wildlife habitat to control this noxious weed.
Photo: Mary Ellen (Mel) Harte, Bugwood.org
Houndstongue is a biennial plant that is eight to 48 inches tall. First year's growth is strictly vegetative with flowering in the second year. In the early summer flowers appear, by late summer or fall burrs appear that reseed by first attaching like Velcro to clothing, animal hair and other objects. Flowers are reddish-purple with a five-lobed corolla. Houndstongue is found throughout western Montana and is increasing in eastern areas of the state to infest nearly 400,000 acres.