Ontario or Bottomland Aster, aster du lac Ontario
Symphyotrichum ontarionis (Wiegand) G. L. Nesom is native to often shaded, usually moist, alluvial soils, alluvial streams or lake shores, floodplain deciduous forests or thickets, bogs, marshes, edges of fields, and roadsides in western Québec to Minnesota south to Alabama and eastern Texas (Brouillet et al. 2006; FNA). The species has been treated as Aster ontarionis Wieg., Aster missouriensis Britt., and Aster pantotrichus Blake. Symphyotrichum ontarionis is often confused with Sy. lateriflorum, from which it can be distinguished by its shorter disc corolla lobes that are yellow (never violet with age) and abaxial leaf surfaces that are either moderately to densely hairy or glabrous to glabrate (var. glabratum) without hairs along midveins (as is typical of Sy. lateriflorum). The species includes diploids 2n=16 (var. glabratum) and tetraploids 2n=32 (var. ontarionis). Semple et al. (2024) reviewed all published counts and presented a cytogeography map for the two varieties.
Two varieties are recognized.
Revised 11 November 2024 by J.C. Semple
© 2024 J.C. Semple, including all photographs unless otherwise indicated
Brouillet, L., J.C. Semple, G.A. Allen, K. Chambers and S. Sundberg. 2006. Symphyotrichum Nees. pp. 465-539. In Flora North America Editorial Committee, eds. Flora of North America. Vol. 20. Asteraceae, Part 2. Astereae and Senecioneae. Oxford University Press, New York.
Semple, J.C., J.G. Chmielewski, A. Bouchard, and L. Brouillet. 2024. The cytogeography Symphyotrichum lateriflorum, S. ontarionis, S. racemosum, and S. tradescantii (Asteraceae: Astereae). Phytoneuron 2024-68: 1–20.