Flower:

Branching cluster of numerous, stalked, daisy-type flowers at the top of the plant and arising from upper leaf axils. Flowers are about ¾ inch across with 10 to 15 petals (ray flowers) surrounding a yellow center disk that turns reddish with age. Ray color ranges from nearly white or pale blue to bright blue or lavender.

Surrounding the base of the flower are 4 or 5 layers of narrow, sharply pointed bracts (phyllaries), the outermost bracts typically green, the inner greenish white at the base with long, diamond shaped green tips. Bracts are hairless except sometimes for minute hairs around the tip edge. Flower stalks are typically under 1/3 inch long with a few, small, leaf-like bracts and may have sparse, spreading hairs.

Leaves and stems:

Leaves are firm, 1 to 4 inches long, ½ to 3 inches across, coarsely to shallowly toothed around the edges, rough-textured on the upper surface, covered in short, soft hairs on the underside, and mostly heart-shaped. Basal and lower stem leaves typically wither away by flowering time, and have long stalks with narrow wings on the sides that form a groove.

As leaves ascend the stem, they become smaller, less heart-shaped with rounder bases, and shorter-stalked but with broader wings. Stems are erect, hairless or nearly so at the base becoming densely short-hairy in the upper plant and into the flower clusters.

Fruit:

Fruit is a dry seed with a tuft of light brown hair to carry it off in the wind.

Notes:

Asters can be difficult to ID. Drummond's Aster is distinguished by a combination of traits: stem densely short-hairy in the upper plant, firm, heart-shaped leaves with toothed edges, a rough texture on the upper surface and densely short-hairy on the lower, narrowly winged leaf stalks in the lower plant and more broadly so above, ¾-inch, short-stalked, blue to lavender flowers with 10 to 15 rays, and a panicle with numerous flowers. Of the other blue/violet asters with heart-shaped leaves, Blue Wood Aster (Symphyotrichum cordifolium), Lindley's Aster (S. ciliolatum),  Short's Aster (S. shortii), and Big-leaf Aster (Eurybia macrophylla) are typically smooth on the upper leaf surface, where Drummond's Aster is rough textured, and of these, only Short's Aster has a densely hairy upper stem but is further distinguished by its mostly toothless and proportionately narrower leaves. Arrowleaf Aster (S. urophyllum) has heart-shaped leaves with narrow wings on the lower stem, but has smaller white flowers.