Northern Prairie Wildlife Research Center
Restricted in distribution in North Dakota to the western one fourth of the State, hoary aster occurs from southern Saskatchewan south to Colorado and California at elevations up to 8,500 feet.
Hoary aster is a taprooted perennial, or possibly biennial, from a woody crown termed a caudex. Plants can have more than one stem, but always have many branches. North Dakota specimens are 6-12 inches tall, but may reach 30 inches in the arid southwest, where the plant is often called "pinyon aster." Leaves are narrow and about one to two inches long, but are reduced to mere bracts at the top of the branches. The ray flowers on the outside of the flower heads are bright bluish-purple to pink. Flower heads can occur singly at the ends of branches or form dense clusters in the upper half of the branches. The tiny achenes (seeds) carry a tuft of white bristles called a pappus.
Look for hoary aster in open dry sites during July to October. Plants seem to prosper under moderate or heavy grazing. There are no known economic uses for the plant.
Hoary aster is a member of the sunflower family (Asteraceae). This is one of the largest families of plants in the world (about 15,000 species) and the largest in North Dakota. There are about 30 species of Machaeranthera in temperate North America. The generic name was derived form the Greek machaira, "sword" and anthera, "anther", in reference to the pointed, pollen-bearing organs. Canescens means "becoming gray" in botanical Latin. Hoary aster was first described for science by the German botanist Frederick Pursh in his monumental Flora Americae Septentrionalis of 1814. Pursh was the first to publish on the many new plants collected by Lewis and Clark.