Cirsium scariosum
Encyclopedia
Cirsium scariosum is a species of thistle
known by the common names meadow thistle and elk thistle. It is native to much of western North America from Canada to Mexico, where it grows in a variety of habitat types. This is a variable species made up of several geographic races, most of which have been previously classified as species. The races intergrade but their morphologies
can also be quite different. This is generally a biennial or perennial herb. It takes three main forms, a stemless, flat rosette with a cluster of flower heads
in the center, a mounding form with a short, erect stem, or a fully erect form reaching up to 2 meters in height. When there is a stem it is usually fleshy, ridged, and woolly in texture. The leaves are sharply toothed or cut into toothed lobes, lined with spines, and up to 40 centimeters at their longest near the base of the plant. The inflorescence
holds several flower heads, each up to 4 centimeters long and 5 wide. The flower head is lined with phyllaries
which may have spines and teeth and filled with white to purple flowers. The fruit is a compressed achene
a few millimeters long topped with a pappus
which may be 3 centimeters in length.
Cirsium
Cirsium is a genus of perennial and biennial flowering plants in the Asteraceae, one of several genera known commonly as thistles. They are more accurately known as Plume thistles. These differ from other thistle genera in having feathered hairs to their achenes...
known by the common names meadow thistle and elk thistle. It is native to much of western North America from Canada to Mexico, where it grows in a variety of habitat types. This is a variable species made up of several geographic races, most of which have been previously classified as species. The races intergrade but their morphologies
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
can also be quite different. This is generally a biennial or perennial herb. It takes three main forms, a stemless, flat rosette with a cluster of flower heads
Head (botany)
The capitulum is considered the most derived form of inflorescence. Flower heads found outside Asteraceae show lesser degrees of specialization....
in the center, a mounding form with a short, erect stem, or a fully erect form reaching up to 2 meters in height. When there is a stem it is usually fleshy, ridged, and woolly in texture. The leaves are sharply toothed or cut into toothed lobes, lined with spines, and up to 40 centimeters at their longest near the base of the plant. The inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
holds several flower heads, each up to 4 centimeters long and 5 wide. The flower head is lined with phyllaries
Bract
In botany, a bract is a modified or specialized leaf, especially one associated with a reproductive structure such as a flower, inflorescence axis, or cone scale. Bracts are often different from foliage leaves. They may be smaller, larger, or of a different color, shape, or texture...
which may have spines and teeth and filled with white to purple flowers. The fruit is a compressed achene
Achene
An achene is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent...
a few millimeters long topped with a pappus
Pappus (flower structure)
The pappus is the modified calyx, the part of an individual disk, ray or ligule floret surrounding the base of the corolla, in flower heads of the plant family Asteraceae. The pappus may be composed of bristles , awns, scales, or may be absent. In some species, the pappus is too small to see...
which may be 3 centimeters in length.