The common name of symphyotrichum porteri
, smooth white aster, refers to the stems and leaves, which are smooth and hairless, and the flowers which are white. Leaves are relatively long, up to 3 inches, but thin, a quarter of an inch or less; they have one or more central veins, a spike at the tip, and edges that are usually entire, but may have tiny teeth towards the end. They grow all the way up the stem, becoming shorter and more linear, often with smaller leaves, or wings, at the base.
Flowerheads are produced on short, leafy stems, forming open, panicular clusters. Flowers typically have between 20 and 34 white ray florets and 40 to 75 yellow to maroon disc florets. The phyllaries are green, hairless, linear and not sticky, with pointed, outwards-curving tips.