Long-leaved aster is an open, branched perennial from a rhizome or branching caudex. It ranges in height from 20-100 cm. The stem leaves are very short and linear, close to the stem. The basal leaves are long and narrow. All leaves are are entire margined and smooth surfaced. The leaves range from 2-10 cm long and 2-20 mm wide.
The flower heads are small with conspicuous outer bracts reflexed outwards. The disk flowers are yellow and the 15-40 ray flowers are pink to lavender and range from 5-15 mm long. Long-leaved aster flowers from July to October.
Long-leaved aster is found in wet to dry habitats, from the lowlands to 3000 meters in altitude.
Long-leaved aster is found mostly east of the Cascades and Sierra Nevada to southern California, east to southeastern Washington, Saskatchewan, and New Mexico.
Long-leaved aster is found in the Columbia River Gorge at the mouth of the Deschutes River.