Submodule 5: Most Common Western Rangelands Weeds

Russian Knapweed

Russian knapweed (Acroptilon repens) is a creeping herbaceous perennial, or forb. The stems of the plant are erect, growing up to 3 feet (1 m) tall. Leaves on the lower part of the plant are often lobed and up to 4 inches (10 cm) long. Upper leaves are generally not lobed (or indented) and are smaller. Flower heads are cone-shaped, about 0.5 inches in diameter, and usually pink to lavender-blue. There are modified leaves called bracts surrounding the flowers. Flowering generally occurs between June and September depending on environmental conditions. Over time, Russian knapweed tends to form dense, single-species stands due to both superior competition for resources and to allelopathy (excretion of chemicals by a plants that deters the growth of neighboring plants).

Russian Knapweed stand (photo courtesy Larry Howery)