About Cirsium brevistylum Cronquist
Cirsium brevistylum Cronquist is a species of thistle with the common names Indian thistle and clustered thistle. It is native to western North America, where it has been documented in southwestern British Columbia, Washington, Oregon, Idaho, Montana, and California. This species grows in moist areas across a wide range of habitat types, from mountain forests to chaparral and coastal marshes. It is an annual or biennial native thistle that typically reaches 200 cm (79 in) in height, and can sometimes exceed 300 cm (9.8 ft) tall. Plants usually produce a single stem, which may branch near the top, and the entire stem is covered in hairs and webby fibers. Its leaves are deeply cut into many lobes edged with twisted teeth; the longest leaves, found near the plant base, reach around 25 centimeters in length. Leaves grow from winged petioles that bear many spines. The inflorescence holds one to many flower heads, which form both at the tips of stem branches and in leaf axils. Each flower head measures roughly 3 centimeters long by 4 centimeters wide, and is lined with cobwebby, bristly phyllaries tipped with spines. The flower head is filled with white or pink flowers that are approximately 2 centimeters long. Its fruit is a brown achene a few millimeters long, topped with a pappus that measures one to two centimeters in length.
