Symphyotrichum hallii

From Puget Prairie Plants
  • Scientific Name: Symphyotrichum hallii
  • Family: Asteraceae
  • Common Names: Hall's aster
  • Synonyms and misapplications: Aster chilensis, Aster hallii
  • Codon: SYMHAL
    Photo 2003 Rod Gilbert


Symphyotrichum hallii
Scientific classification
Kingdom: Plantae
Subkingdom: Tracheobionta
Phylum: Spermatophyta
Subphylum: Magnoliophyta
Class: Magnoliopsida
Subclass: Asteranae
Order: Asterales
Family: Asteraceae
Genus: Symphyotrichum Nees
Species: Symphyotrichum hallii A. Gray


Rhizomatous perennial, one to many radiate heads in wide-branching bracteate inflorescences. Inflorescences generally white. Inflorescence bracts generally much smaller than upper stem leaves, involucres 4-7mm high, phyllaries generally bi-colored, papery below and green above, and spreading or slightly recurved to ascending. Lower leaves petiolate and pubescent, upper leaves sessile and usually pubescent.[1][2]

Distinguished from the common Symphyotrichum subspicatum, S. foliaceum, and S. spathulatum by its strongly graduated involucre and outer involucral bracts that are markedly shorter than the inner ones, obtuse and not leaflike. Symphyotrichum ascendens and S. chilense are distinguished by the bracts of their inflorescences, which if present, are mostly erect, greater than 4 times as long as wide, and markedly acute; their rays are usually blue or pinkish (sometimes white).[3]

Bloom Period



Restricted to seasonally wet grasslands and remnant prairies of the Puget Trough of Western Washington and the Willamette Valley, with outlying populations in the Columbia Gorge and Eastern Washington. Threatened in Washington State.[4] S. hallii is ranked critically imperiled by NatureServe. It is rarely found on the South Salish Prairies, but historical herbaria collections show its range in the state to have spanned from the San Juan Islands to near the Columbia River in prairies.[5]


Remnant prairie, seasonally wet grasslands.[2]

Associated species include snowberry (Symphoricarpos albus), colonial bentgrass (Agrostis capillaris), goldenrod (Solidago lepida var. salebrosa), white-top aster (Sericocarpus rigidus), Douglas aster (Symphyotrichum subspicatum), and oxeye daisy (Leucanthemum vulgare).[3]


Symphyotrichum hallii is an important late-summer nectar source for butterflies.[5]

Photo Gallery


  1. WTU Herbarium, Burke Museum, & University of Washington. (n.d.). Retrieved from
  2. 2.0 2.1 Hitchcock, C. L., Cronquist, A., Giblin, D., & Legler, B. et al. (2018). Flora of the Pacific Northwest: an illustrated manual. Seattle: University of Washington Press.
  3. 3.0 3.1 Rare Plant Field Guide: WA - DNR. Retrieved from
  4. Gilbin, D., Burke Museum, & University of Washington. (n.d.). Symphyotrichum hallii . Retrieved from hallii
  5. 5.0 5.1 Bowcutt, F., & Hamman, Sarah. (2016). Vascular plants of the South Sound prairies (First ed.). Olympia, Washington: The Evergreen State College Press.