Distribution: West of Cascades crest in Washington; Southern California and Arizona, Minnesota, Iowa, Missouri, Wisconsin, Michigan, Illinois, Indiana, New York, Maine, Vermont, New Hampshire, Massachusetts, Rhode Island, Connecticut; west of Cascades in British Columbia, northeastern Canada.
Habitat: In forest.
Substrate: On bark, esp. hardwood.
Conservation Status: Not of concern
Thallus white to pale green, occurring in small patches. Ascomata black, branching, <1.5 mm in length, 0.1-0.2 mm in width, forming asteriated clusters.
PNW Herbaria: Specimen records of Arthonia radiata in the Consortium of Pacific Northwest Herbaria database
CalPhotos: Arthonia radiata photos