aster hallii

Flowers of the Sequalitchew Prairie

aster hallii

State Threatened Flower, DNR

Status: State Threatened
Rank: G4S1
General Description: Adapted from Douglas et al. (1998): A fibrousrooted perennial 8 to 40 in. (20 to 100 cm) tall from a rhizome or short,
thickened, woody caudex. The stem is pubescent at least above. The
linear leaves are mostly entire and hairless to more or less pubescent.
The lower leaves are usually oblanceolate, petiolate, and commonly
deciduous except in smaller plants. The middle and upper leaves are
sessile, linear to obovate or oval, ¾ to 4 in. (2 to 10 cm) long, and 1/16
to ¾ in. (2 to 20 mm) wide. The inflorescence is conspicuously
divaricate-bracteate. There are one to many floral heads in the inflorescence with an involucre that is ¼ in. (5 to 7 mm) high, and has
overlapping bracts, which are green-tipped, mostly obtuse or acutish
and 2 to 4 times as long as wide. There are most often 15 to 40 white
rays that are ¼ to 2/3 in. (5 to 15 mm) long.

Identification Tips: Aster hallii can be distinguished from the common A. subspicatus, A. foliaceous, and A. occidentalis by its strongly
graduated involucre. The outer bracts of the involucre are also obtuse,
markedly shorter than the inner, and not foliaceous. In the Flora of the
Pacific Northwest, A. hallii is described as a subspecies of A.
chilensis (A. chilensis spp. hallii), along with ssp. chilensis and ssp.
ascendens. To distinguish these subspecies (now described as full
species) use the following characteristics: the inflorescence of A. hallii
is conspicuously divaricate-bracteate, its bracts are mostly obtuse or
acutish, 2 to 4 times as long as wide, and markedly acute, its rays are
white, its leaves are linear, and its heads are generally smaller than in
other subspecies. The inflorescence of A. chilensis and A. ascendens
are not conspicuously divaricate-bracteate, their bracts, if present, are
mostly erect, more than 4 times as long as wide, and markedly acute,
their rays are usually blue or pinkish (sometimes white), and their
leaves are linear or broader than A. hallii. Use of a technical key is
necessary for correct identification.

Phenology: Flowers from July to October.

Range: Found in Oregon, and occasionally Thurston and Clark
Counties, Washington.

Habitat: Aster hallii prefers dry, open places in valleys and plains. In
Washington, this species has been seen in a wet remnant prairie in a
floodplain.