Symphyotrichum hallii

{{Short description|Species of flowering plant in family Asteraceae}}

{{Use dmy dates|date=July 2021}}

{{Use shortened footnotes|date=July 2021}}

{{Use American English|date=July 2021}}

{{Speciesbox

| image = Symphyotrichum hallii 24066847.jpg

| status = G4

| status_system = TNC

| status_ref = {{sfn|NatureServe|2021}}

| range_map = Symphyotrichum hallii distribution.png

| range_map_alt = Symphyotrichum hallii native distribution: Oregon and Washington — Puget Sound region, Willamette Valley, outliers in Columbia Gorge and central Washington. County distribution: Oregon — Benton, Clackamas, Douglas, Hood River, Josephine, Lane, Linn, Marion, Multnomah, Polk, and Wasco; Washington — Clark, King, Okanogan, and Skagit.

| range_map_caption = Native distribution{{sfn|USDA, NRCS|2014}}

| genus = Symphyotrichum

| display_parents = 5

| parent = Symphyotrichum sect. Occidentales

| species = hallii

| authority = (A.Gray) G.L.Nesom{{sfn|POWO|2019}}

| synonyms_ref = {{sfn|POWO|2019}}

| synonyms =

{{Species list

| Aster chilensis subsp. hallii | (A.Gray) Cronquist

| Aster hallii | A.Gray

|}}

}}

Symphyotrichum hallii (formerly Aster hallii) is a species of flowering plant in the family Asteraceae endemic to western Oregon and Washington states. Commonly known as Hall's aster, it is a perennial, herbaceous plant with a long rhizome that creates colonies of itself. It grows about {{convert|30-60|cm|ft|0|abbr=off|sp=us}} tall, and has white (sometimes pale violet) rays that open July–August.{{sfn|Brouillet|Semple|Allen|Chambers|2006}}

Most occurrences of the species have been found at elevations of {{convert|0–500|m|ft|-1|abbr=off|sp=us}} in open areas in the Puget Sound region and Willamette Valley, with outliers in Columbia Gorge and central Washington.{{sfn|Brouillet|Semple|Allen|Chambers|2006}} It is conservationally Imperiled (S2) in Washington state.{{sfn|NatureServe|2021}}