Small White Asters

Small White Asters
Small White Asters. Symphyotrichum various species.
Asteraceae, the daisy, sunflower, or composite family.

Plant: Erect, branching stems, 1'-4' high, with loose terminal clusters of small, white, daisy-like flower heads. Perennial.
Flowers: Small, white flower heads, generally 1/2" or less, generally with 15-35 rays, and yellow centers that turn dark with age in some species.
Leaves: Alternate, narrowly ovate to lanceolate-linear, margins smooth to sparsely toothed, surfaces smooth to hairy, sessile in most species. Leaves on flower stems my be very small, bract like; lower leaves 2"-4" or more.
Fruit: A globular head of achenes with silky white hairs
Blooming: August-November
Habitat: Fields, waste areas, clearings.

Comments: There is a group of several small, white asters in our area that are difficult to distinguish, that are quite variable, and that probably hybridize to some extent. There does not seem to be any strong botanical consensus on the species breakdown either, though modern tendency has been to reduce the number of recognized species. In a given area, several different-looking forms can generally be found, varying in the size and shape of the involucral bracts, the hairiness of stems and leaves, the size and placement of leaves etc. Conditions can make a large difference. A plant growing in a dry location in full sun may have leaves very different from the same plant growing in a shadier, moister location. These species were formerly placed in the genus Aster, but have been moved to the new genus Symphyotrichum on the basis of recent genetic studies. Species found in our area include the following:
White Heath Aster (S. erichoides) has small, linear leaves, and flower heads on individual, leafy stalks.
Awl Aster (S. pilosum) is similar, but with hairy leaves.
Small White Aster (S. racemosum) has larger, more lanceolate leaves, and flower heads often in small clusters with several on one stalk. It sometimes grows in wood margins in partial shade.
Calico Aster (S. lateriflorum) has flower heads with fewer rays (6-15) than most other species described here, and centers that quickly turn pink (though it is not the only variety with centers that darken). The stem leaves are more broadly lanceolate, with often winged petioles in contrast to the species above whose leaves are almost always sessile. It often grows in partial shade or open wooded areas.
Purplestem Aster White Form (S. puniceum) is a larger-flowered (3/4" or more), larger-leafed plant with open clusters of flower heads that are usually light blue to violet, but which can be white.
White Wood Aster (Eurybia divaricata) also has open clusters of smallish, white flower heads with centers that turn pink, but otherwise is a quite different plant in a separate genus. The leaves are large, heart-shaped, coarsely toothed, and stalked, quite different than the mostly narrow, sessile, and toothless leaves of the Symphyotrichum species, and it grows in shady, wooded environments.

Where to find them: Common in open, sunny areas of the park, often mixed with larger blue/violet-flowered asters and goldenrod. Sometimes in shadier wood-margin areas as well.