Scientific NameArctium tomentosum
These robust plants grow to 3 m in height and are umbrella-shaped with flower heads at the tips of the branches. It produces a large fleshy tap root during the first year of life. Stems are red and green striped.
The first year of growth is a basal rosette. The leaves of the rosette are usually 45 cm long by 40 cm wide and are white and woolly beneath. The mature plants leaves are alternate and smaller in size toward the top of the plant. Leaves are ovate with a heart-shaped base.
Floral bracts are covered with soft hairs that spread at maturity (florets have sticky hairs). The hooked bristles on the floral bracts aid in the dispersal of seeds.
Flower Seed Head
Flowers can be found at the ends of branches in rounded or flat toped clusters. The clusters, 3 - 4.5 cm across, consist of purple disk florets surrounded by overlapping hooked bracts (like velcro).
An achene containing a single seed is approximately 6mm long. The seed a mottled brown club-shape is 5-6.5 mm long with barbed yellow bristles. Plants are capable of producing 12,000 seeds that remain viable for up to 3 years.
This plant is often found in fence lines, waste areas, and stream banks throughout Canada and the northern two-thirds of the United States.
upright and nonwoody
Thorns or Spines
Approximate Flower Diameter
Dominant Flower Color
shorter than leaf
Stem Cross Section
round or oval