Symphyotrichum frondosum (formerly Aster frondosus) is a species of aster known by the common name short-rayed alkali aster. It is native to much of western North America from British Columbia and the Cascade Range, the Sierra Nevada, Transverse, and Peninsular Ranges in California, the Rocky Mountains, to Arizona and New Mexico, where it grows in wet habitat such as marshes and meadows, especially in alkaline or saline conditions. Symphyotrichum frondosum is an annual or occasionally perennial herb growing a leaning or erect stem to a maximum height between 20 and 60 centimeters. The leaves are a few centimeters long and oval in shape with rounded tips. The stem and leaves are mostly hairless. The inflorescence is a small array of flower heads containing many short pale pink or lavender ray florets and yellow disc florets. The fruit is a hairy achene with a bushy tawny pappus.