BC Conservation Data Centre: Species Summary
Symphyotrichum frondosum
short-rayed aster
| Scientific Name: | Symphyotrichum frondosum (Nutt.) Nesom | ||||||||||
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| Scientific Name Synonyms: |
Aster frondosus
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| English Name: | short-rayed aster | ||||||||||
| Classification / Taxonomy | |||||||||||
| Scientific Name - Concept Reference: | Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR. | ||||||||||
| Classification Level: | Species | ||||||||||
| Species Group: | Vascular Plant | ||||||||||
| Species Code: | SYMPFRO | ||||||||||
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| Conservation Status / Legal Designation | |||||||||||
| Global Status: | G4 (Feb 2025) | ||||||||||
| Provincial Status: | S2 (Apr 2019) | ||||||||||
| BC List: | Red | ||||||||||
| Provincial FRPA list: | |||||||||||
| Provincial Wildlife Act: | |||||||||||
| COSEWIC Status: | Endangered (Apr 2006) | ||||||||||
| SARA Schedule: | 1 - Endangered (Dec 2007) | ||||||||||
| General Status Canada: | 1 - At Risk (2010) | ||||||||||
| Ecology & Life History | |||||||||||
| General Description: | Alkali Aster is an annual with solitary, branched stems which are 5-60 cm high and arise from a taproot. The alternate, linear leaves have entire margins and are up to 6 cm long. Lower leaves have petioles, but become sessile higher up. Foliage is glabrous. Flower heads are borne in open, branched inflorescences arising from the leaf axils. Each flower head has 2-3 series of green, overlapping, lance-shaped involucral bracts which are 5-9 mm long. There are yellow disk flowers and numerous pinkish, filiform rays, which are 2-4 mm long. Each achene has a pappus consisting of numerous soft bristles on top that are longer than the disk flowers. | ||||||||||
| Technical Description: | |||||||||||
| Diagnostic Characteristics: | This species is very similar to the more common A. BRACHYACTIS, but the latter has rays that are less than 2 mm long or are lacking. A. FRONDOSUS might also be confused with ERIGERON ACRIS or E. LONCHOPHYLLUS, but the latter 2 have only 1 main series of involucral bracts. A hand lens and technical key will probably be required for positive identification. | ||||||||||
| Identification Comments: | An annual herb 5-60 cm tall, stems much branched, usually decumbent but sometimes erect, arising from a taproot (Douglas et al. 1998b). Heads usually very numerous in paniculate inflorescences. Ray flowers 1.5 - 2 mm long, barely exceeding the disk flowers, pink to white in living specimens, drying to white. Involucral bracts 5 - 9 mm tall, subequal to moderately graduated, obtuse. Leaves alternate on the stem and linear in shape. Lower leaves petioled, becoming sessile towards the top of the plant. Seeds achenes with numerous short bristles on top (COSEWIC 2006e; Klinkenberg et al. 2007). Chromosomes n=7 (Houle and Brouillet 1985). | ||||||||||
| Similar Species: | Symphyotrichum ciliatum similar to S. frondosum and is distinguished by its lack of ray petals (COSEWIC 2006e; Klinkenberg et al. 2007). | ||||||||||
| Provincial Reproduction Comments: | Dispersal is probably mediated by wind, water, waterfowl, and small mammals (COSEWIC 2006e). Brouillet (pers. comm. 2005) indicated that Symphytotrichum frondosum is autogamous, in part, with little genetic exchange among distant populations. Seed banks are critical to the survival of shoreline species after periods of high water levels because it enables regeneration during subsequent periods of low water (Keddy and Reznicek 1982, 1986). The occurrence of ephemeral populations in Surrey and New Westminister suggests that S. frondosum is capable of long-distance dispersal, presumably by river currents but possibly by wind or waterfowl (COSEWIC 2006e; Klinkenberg et al. 2007). It is also possible that materials containing S. frondosum seeds could have been transported by humans. | ||||||||||
| Provincial Ecology Comments: | Symphytotrichum frondosum can withstand high pH and high salinity but prefers moist habitats (Munz and Keck 1959). It is adapted to fluctuating water levels and late summer drawdown (COSEWIC 2006e; Klinkenberg et al. 2007). One Canadian subpopulation was found on a drier beach adjacent to the drawdown zone, and Wiggins (1980) reported that it can occur in drier sites. Seed banks are critical to the survival of shoreline species after periods of high water levels because it enables regeneration during subsequent periods of low water. Periodic high water is also essential to the survival of shoreline species because it reduces invasion by competing upland species (Keddy and Reznicek 1982, 1986). | ||||||||||
| Habitats: (Type / Subtype / Dependence) |
Other Unique Habitats / Alkali Ponds/Salt Flats / Obligate
Wetland / Bog / Obligate Wetland / Fen / Obligate Wetland / Marsh / Obligate Wetland / Swamp / Obligate |
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| Global Habitat Comments: | Symphyotrichum frondosum grows in "moist, usually saline soils, summer-receding shores of lakes or ponds, vernally moist, alkaline bottoms, marshes, often in steppes" (FNA 2006). | ||||||||||
| Provincial Habitat Comments: |
Habitat for Symphytotrichum frondosum in BC is lakeshores in the Bunchgrass biogeoclimatic zone of sagebrush steppe in the southern Okanagan Valley (Douglas et al.1998b), and disturbed, dredged sand spoils along the lower Fraser River (COSEWIC 2006e; Klinkenberg et al. 2007). Hydrology at all sites varies with seasonal precipitation, and some sites have remained dry for three years or more (COSEWIC 2006e). Preferred habitat is moist with low nutrient availability, but S. frondosum can tolerate high pH and high salinity (Munz and Keck 1959; Wiggins 1980). Symphytotrichum frondosum is a late emergent (August-September) shoreline species occurring in full sun or partial shade primarily just below the mean summer water line. It occurs in moist drawdown zones of sandy beaches and in saline zones around the perimeters of alkali lakes and ponds, becoming exposed in late summer and early fall. Klinkenberg et al. (2007) also reported it from drier sand beach adjacent to drawdown zones. In general, suitable habitat occurs throughout the southern portion of the Okanagan Valley. Associated native plants include alkali-tolerant Symphyotrichum ciliatum and Distichlis spicata var. stricta. Douglas (1999) reported several SARA-listed species associated with S. frondosum, including Rotala ramosior, Ammannia coccinea, Eleocharis acicularis, Cyperus aristatus, Eleocharis atropurpurea, and Lipocarpha micrantha. Associated exotic species include Phalaris arundinacea, Plantago major, Poa annua, Chenopodium glaucum, Lythrum salicaria, Melilotus alba, and Polygonum aviculare (COSEWIC 2006e). |
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| Provincial Phenology: (1st half of month/ 2nd half of month) |
May: / Germinating
Jun: Germinating / Germinating Jul: Vegetative, Germinating / Vegetative, Germinating, Flowering Aug: Vegetative, Germinating, Flowering / Vegetative, Flowering Sep: Vegetative, Flowering, Fruiting / Vegetative, Flowering, Fruiting Oct: Flowering, Fruiting / Fruiting Nov: Fruiting / Fruiting |
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| Provincial Phenology Comments: | Plants are generally submersed until late summer. Germination has been observed in May or June when the water levels drop, although it is possible it may occur earlier. Flowering occurs from late July to early October. At Vaseux Lake in mid October of 1999, all plants were small with mature fruit (COSEWIC 2006e; Klinkenberg et al. 2007). | ||||||||||
| Elevation (m) (min / max): | Provincial: 279 / 340 | ||||||||||
| Known Pests: | |||||||||||
| Pollen Vector: | |||||||||||
| Pollinator: | |||||||||||
| Dispersal: | |||||||||||
| Provincial Inventory | |||||||||||
| Inventory Priority: | B - Strong | ||||||||||
| Ownership of occurrences (Known locations): | Mixed private/government | ||||||||||
| Inventory Need: | Most of the eastern shoreline of Osoyoos Lake has not been searched and additional populations may occur in this relatively undeveloped section, although development plans are underway. Because Symphytotrichum frondosum has been documented twice in the lower Fraser Valley, field work is required further upstream to identify source populations, particularly in the Bunchgrass and Interior Douglas-fir (BEC) biogeoclimatic zones within the Thompson-Nicola Regional District. Populations of S. frondosum in Washington extend across the width of the state (from Cowlitz County to Spokane), indicating that additional inventory in BC should focus not only in the Fraser and Thompson river valleys but also the Interior Douglas-fir BEC zones east and west of the Okanagan area (Klinkenberg et al. 2007). | ||||||||||
| Inventory Comments: | Fieldwork in BC was conducted in the Okanagan in 2002, 2003, and 2007. Known populations were checked and confirmed at Vaseux and Skaha Lakes. Intensive targeted searching of most saline lake and pond shorelines was conducted between Osoyoos and Salmon Arm. Indian Reserve lands on the east shoreline of Osoyoos Lake were not searched, but additional populations of Symphytotrichum frondosum have been reported from there. Searches were timed so that sufficient drawdown would have occurred to expose lakeshore habitat. For the most part, most lakes and ponds had receded considerably by the time searches were conducted each year; but lake levels were not at their minimum and more plants may yet be found in some spots. The discovery of the population at Max Lake in the second week of September 2003 indicates additional searching for the species is warranted. Sections of shoreline of the following lakes were checked: Deadman Lake, Gallagher Lake, Mahoney Lake, Okanagan Lake (including Sun Oka Provincial Park), Osoyoos Lake, Prather Lake, Shannon Lake, Skaha Lake, Tugulnuit Lake, Twin Lakes, Vaseux Lake, White Lake, and others, plus associated wetlands. Limited searches were done in the lower Fraser River valley in 2002-2004 (COSEWIC 2006e). | ||||||||||
| Economic Attributes | |||||||||||
| Provincial Economic Comments: | No commercial or cultural uses are known for Symphytotrichum frondosum (COSEWIC 2006e). Protecting populations of this species as part of the recovery planning process may have socioeconomic considerations in the Osoyoos Lake area where some site development has been proposed (Klinkenberg et al. 2007). | ||||||||||
| Distribution | |||||||||||
| Endemic: | N | ||||||||||
| Global Range Comment: | Symphyotrichum frondosum occurs in western North America from British Columbia, Canada and Idaho and Wyoming in the United States south to New Mexico to California and Baja California, Mexico (FNA 2006). It was introduced in Maine through wool waste (Native Plant Trust 2025). Native range extent was estimated to be approximately 1.7 million square kilometers using herbarium specimens, photo-based observations, and NatureServe Network occurrence data documented between 1994 and 2025 (GBIF 2025, iNaturalist 2025, NatureServe 2025, SEINet 2025). | ||||||||||
| Disjunct, more common elsewhere: | N | ||||||||||
| Peripheral, major distribution elsewhere: | Y | ||||||||||
| Authors / Contributors | |||||||||||
| Global Information Author: | JM (1994), rev. Soteropoulos (2025) | ||||||||||
| Last Updated: | Feb 04, 2025 | ||||||||||
| Provincial Information Author: | Christy, John A. | ||||||||||
| Last Updated: | Mar 15, 2008 | ||||||||||
| Last Literature Search: | |||||||||||
| References and Related Literature | |||||||||||
B.C. Ministry of Environment. Recovery Planning in BC. B.C. Minist. Environ. Victoria, BC. |
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COSEWIC. 2006e. COSEWIC assessment and status report on the short-rayed alkali aster Symphyotrichum frondosum in Canada. Comm. on the Status of Endangered Wildl. in Can. Ottawa. vi + 22 pp. |
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Douglas, G.W., F. Lomer, and H. Roemer. 1998. New or Rediscovered Native Vascular Plant Species in British Columbia. Can. Field-Nat. 112(2):276-279. |
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Douglas, G.W., G.D. Straley, and D. Meidinger, eds. 1998b. Illustrated Flora of British Columbia, Vol. 1, Gymnosperms and Dicotyledons (Aceraceae through Asteraceae). B.C. Minist. Environ., Lands and Parks, Wildl. Branch, and B.C. Minist. For. Res. Program. 436pp. |
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Douglas, George W. 1999. Status of toothcup in British Columbia. Wildlife Bulletin no. B-94. BC Minist. of Environ. Lands and Parks and Resources Inventory Branch, Victoria, BC. |
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Flora of North America Editorial Committee (FNA). 2006b. Flora of North America north of Mexico. Vol. 20. Magnoliophyta: Asteridae, part 7: Asteraceae, part 2. Oxford Univ. Press, New York. xxii + 666 pp. |
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Houle, F. and L. Brouillet. 1985. Chromosome number determinations in Aster section Conyzopsis (Asteraceae). Brittonia 37(4): 369-412. |
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Keddy, P.A. and A.A. Reznicek. 1982. Seed banks and persistent relict shoreline flora. BioScience 32: 132-133. |
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Keddy, P.A. and A.A. Reznicek. 1986. Great Lakes vegetation dynamics: the role of fluctuating water levels and buried seeds. J. of Great Lakes Res. 12(1): 25-36. |
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Klinkenberg, Brian, et al. 2007. Draft Recovery Strategy for the Short-rayed Alkali Aster (Symphyotrichum frondosum) in British Columbia. Prepared for the BC Minist. of Environ., Victoria, BC. |
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Munz, P.A. and D.D. Keck. 1959. A California Flora. University of California Press, Berkeley, CA. |
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Wiggins, I.L. 1980. Flora of Baja California. Stanford Univ. Press, Stanford, California. 1025 pp. |
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Please visit the website Conservation Status Ranks for definitions of the data fields used in this summary report.
Suggested Citation:
B.C. Conservation Data Centre. 2025. Species Summary: Symphyotrichum frondosum. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 10, 2026).