Flower:

Branching clusters, typically flat-topped, of 8 to 90 stalked flowers at the top of the stem. Flowers are ½ to 1¼ inch across with 9 to 20 narrow, pale blue to violet or nearly white petals (ray flowers) irregularly spaced around the small, yellow, center disk. The disk flowers turn reddish brown with age.

Surrounding the base of a flower are hairy, appressed bracts in 4 to 6 layers. Bracts are green or tinged purple, have whitish edging, and are generally oblong with a blunt tip. Flower stalks are up to 1½ inches long, stiff and covered in short glandular hairs.

Leaves and stems:

Leaves are firm, coarsely toothed, surfaces hairless to sparsely hairy and more densely hairy along major veins on the underside. Lowest leaves are large and heart-shaped, up to 8 inches long and 6 inches wide, on long stalks, becoming progressively smaller, more egg-shaped, and shorter stalked as they ascend the stem, with the uppermost leaves reduced to stalkless bracts. Flowering plants have basal leaves that wither away by flowering time; the basal leaves of non-flowering plants may persist longer.

Leaf stalks are narrowly to broadly winged, becoming more pronounced as leaves ascend the stem, the middle to upper leaves often with a pair of small lobes (auricles) at the base of the stalk that clasp the stem. Stems are erect, stiff, unbranched, hairless to sparsely hairy. Plants can create sizable, dense colonies from branching rhizomes.

Fruit:

Fruit is a dry seed with a tuft of dull yellowish brown to orange-brown hairs to carry it off in the wind.

Notes:

Large-leaved Aster, formerly Aster macrophyllus, is a common sight in Minnesota's woodlands and forests, the tell-tale carpet of large, heart-shaped basal leaves seen in early to mid summer a sign of things to come. The large lower and basal leaves are the most recognizable characteristic, particularly the density of any given population, and distinguish this from other blue-flowered asters that may be found in woodland habitats.