Cirsium altissimum
Cirsium altissimum is a North American species of plants in the tribe Cardueae within the family Asteraceae. Common names are tall thistle or roadside thistle. The species is native to the eastern and Central United States.
Description
Cirsium altissimum is, as the name implies, a tall herb, sometimes reaching as much as in sunny areas and in the shade. It is a biennial or perennial plant, blooming only once before dying.In its first year, the plant appears as a rosette of leaves, slightly hairy, with small spines along the leaf margins. The rosette measures up to about across. The plant has a long slender taproot, measuring or more. In its second year, the plant starts as a rosette of leaves with longer hairs than the previous year, plus stout spines. In addition to the previous year's tap root, there are now shallow, sinewy, radiating roots. The second year plant grows tall, tough stems that are densely covered with stiff hairs. Large plants have some branches along the upper portion of their stems. The leaves along the stem are alternate and measure up to long and wide. Leaves vary in shape, with larger leaves generally lanceolate, and smaller leaves elliptic. They could be uncut to deeply pinnately lobed, varying from plant-to-plant and even on the same plant. There is often a spine at the pointed tip of each lobe or dentate tooth. Leaves have flattened white hairs on their upper surface and a dense mat of white-woolly hairs on their lower surface. They are sessile or clasp the stem slightly.
Sometimes there is only one flower head but more often there are more, with pink or purple disc florets but no ray florets. Flower heads are up to across.