Often Thimbleweed (Anemone virginiana) is overlooked when its white flowers are blooming during the summer, but its seed head is rarely missed in the fall. When flowering, stamens surround a green cone that elongates into a cylindrical fruit twice as long as it is wide, giving this member of the Buttercup family its name. The seeds mature in the fall, and the style, part of the female reproductive structure that remains attached to the developing seed, develops a woolly texture, turning the “thimble” into a ball of fluff. A close look reveals that this “cottonball” consists of many tiny dark seeds, each of which bears a cottony tuft to enhance its dispersal by the wind.
Thimbleweed produces chemicals which inhibit seed germination and seedling growth in many species of plants, so often the ground is relatively bare around this plant. Mammalian herbivores usually leave Thimbleweed alone because the foliage contains a blistering agent that can irritate the mouth parts and digestive tract.