Symphyotrichum ascendens (formerly Aster ascendens) is a species of aster known by the common names western aster and longleaf aster. It is native to western North America from British Columbia to Saskatchewan to Arizona and New Mexico, where it grows in many types of habitat, including disturbed areas. This is a rhizomatous perennial herb growing a branching, erect stem to heights between 20 and 60 centimeters. Leaves are widely lance-shaped to oblong and pointed, the largest ones near the base of the stem reaching up to 15 centimeters long. The stem and leaves are roughly hairy in places. The flower cluster is an array of many flower heads with many narrow violet to nearly white ray florets around a center of golden disc florets. The fruit is a hairy achene with a long pappus.