Guide to small white asters
(occasionally pale blue/purple)

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These species have 15 rays or fewer on each flower:

Symphyotrichum lateriflorum - calico aster, goblet aster. Flowers bear 9 to 14 rays; centers are pale yellow, not orange-yellow as in other species. They turn pink-purple as they age. Leaf undersides are hairless, except at the veins; plant stems grow in clumps.

Symphyotrichum ontarione - Ontario aster, bottomland aster. Disc flowers are deeply cut and slightly recurved, upper stem and lower leaf surfaces are uniformly pubescent. Rays are somewhat recurved, exposing the relatively large yellow orange centers more fully. Flowers have 9 to 15 rays. Stems may sprout numerous lateral shoots, whose leaves are somewhat rounded, definitely not linear. Plants are colonial.

Symphyotrichum undulatum - wavy-leaved aster, clasping heart-leaved aster. Unlike most of the smaller, often white, asters, this species has heart-shaped lower leaves. Leaf petioles are expanded at the base, clasping the stem. Leaf edges are wavy; 8 to 15 rays.

These species typically have up to 30 or 35 rays on some flowers:

Symphyotrichum dumosum - long-stalked aster, bushy aster. Flowers with 13 - 30 rays, each set terminally on a petiole or small branch, giving them a separated appearance. 

Symphyotrichum lanceolatum - panicled aster. Prefers wet fields, damp soils. Flowers are mostly white, with 20 - 40 rays each.

Symphyotrichum pilosum - frostweed aster, old field aster. Very common, grows bushy, flowers have 16 - 35 rays. Phyllaries (green sepals under each flower) are pointed and slightly recurved, unlike others species.

Symphyotrichum racemosum - small white aster, small-headed aster. Flowers are noticeably smaller than other species listed here, with 15 to 30 rays each. Stem leaves are long and pointed.

​Guide to larger blue/purple asters
(flowers may be pale or white)

Symphyotrichum cordifolium (formerly Aster cordifolius) - heart-leaved aster, blue wood aster. May be very pale or white. Lower leaves are heart shaped, but leaf petioles are either not winged or very narrowly winged.

​Symphyotrichum lowrieanum (formerly Aster lowrieanus) - Lowrie's aster. Lower leaves are heart-shaped and feature a flared, winged petiole. 

Symphyotrichum novae-angliae (formerly Aster novae-angliae) - New England aster. A stout plant, standing to to six feet, with two-inch purple flowers. Discs are bright yellow. Leaves are rough and clasping.

Symphyotrichum pratense - silky aster. Rare plant of dry barrens, with 1 1/2 inch flowers on thin branching stems. Leaves are narrow with short white hairs on both surfaces.

Symphyotrichum patens (formerly Aster patens) - late purple aster, spreading aster, clasping aster. Blue-purple flowers are usually borne singly; oblong leaves are clasping the entire length of the stem.

​Symphyotrichum shortii (formerly Aster shortii) - Short's aster, blue heart-leaved aster. Characterized by long, heart-based leaves, on thin petioles.