Symphyotrichum frondosum (Nutt.) G.L. Nesom
short-rayed aster (alkali aster)
Asteraceae (Aster family)

Introduction to Vascular Plants


© Brian Klinkenberg     (Photo ID #199)


E-Flora BC Static Map

Distribution of Symphyotrichum frondosum
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Alkali aster is an annual, tap-rooted member of the Asteraceae that is found only in North America, from British Columbia south to Utah, Arizona, New Mexico, California, and Mexico. In BC, it occupies shorelines of lakes and saline ponds in the Okanagan. Flora North America describes it as occurring in "moist, usually saline soils, summer-receding shores of lakes or ponds, vernally moist, alkaline bottoms, marshes, often in steppes, 10–2200 m". It is a late-summer flowering species that is ecologically tied to natural fluctuations in water levels. Flowering and germination occur following summer drawn down of pond and lake levels. Alkali aster is a seed banking species. It may be confused with the similar Symphyotrichum ciliatum (rayless alkali aster), but can be distinguished from that species when in flower by the presence of ray petals. Separation after flowering is more difficult. The earliest collection for alkali aster in the UBC Herbarium was by John Eastham (July 1939) from the shoreline of Osoyoos Lake. It has since been collected by Frank Lomer (1993) and George Douglas (1995), also from Osoyoos Lake. Vagrant, ephemeral single plants have been collected by Lomer from sand dredging piles in Surrey (Lomer pers. comm.2007), indicating that as yet undiscovered populations occur upstream. This species was once more abundant in the Osoyoos Lake area prior to lake level management.

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Species Information

Annual herb from a taproot; stems decumbent to erect, much branched, more or less glabrous, 10-60 cm tall.
Basal leaves soon deciduous; stem leaves linear to oblanceolate, stalked below to unstalked above, 2-6 cm long, 5-10 mm wide, entire, glabrous or fringed with stiff hairs on the margins.
Heads with ray and disk flowers, several to numerous in an open or spikelike, branched inflorescence; involucres 5-9 mm tall; involucral bracts subequal to moderately graduated, linear-lanceolate to linear spoon-shaped, the inner pale-margined, the outer leafy, the tips obtuse; ray flowers white, drying pinkish to pink-purple, 1.5-2 mm long, barely exceeding the disk flowers; disk flowers yellow.
Achenes appressed-hairy; pappus white, surpassing the disk flowers.
Although this species was first collected in 1939 and reported by Eastham (1947) from the Okanagan Valley, it was not recollected again until 1993 along Osoyoos Lake.

SourceThe Illustrated Flora of British Columbia


If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.

Habitat and Range

Moist lakeshores in the steppe zone; rare in SC BC, known recently only from Osoyoos Lake; S to UT, AZ, NM and CA.

SourceThe Illustrated Flora of British Columbia


Synonyms and Alternate Names:
Aster frondosus (Nutt.) Torr. & A. Gray
Brachyactis frondosa (Nutt.) A. Gray
Tripolium frondosum Nutt.

Taxonomic Notes

This species should be searched for in other parts of the Okanagan-Similkameen.