Symphyotrichum falcatum

Western Heath Aster, White Prairie Aster

Symphyotrichum falcatum (Lindl.) G.L. Nesom is native to dry soils, plains, hills, prairies, stream banks and slopes, edges of alkali lakes and flats, roadsides, along railroad rights-of-way, stream banks of prairies, plains and mesic montane habitats from the Alaska to Wisconsin southin the Rocky Mountains and on the Great Plains to Arizona and Texas and adjacent Mexico (Brouillet et al. 2006 FNA).  The species is distinguished from S. ericoides by it generally more open fewer headed inflorescence with larger heads with more florets: involucres (4.5–)5–8 mm; ray florets (15–)20–35, laminae (8–)18–30 mm; disc corollas 2–2.5 mm, lobes 0.7–1.2; cypselae 2–2.5 mm; pappi 4.5–6 mm.  Diploids of S. falcatum can be difficult to separate from polyploid S. ericoides. The species includes diploids (2n=10), tetraploids (2n=20), hexaploids (2n=30) and possibly octoploids (2n=40).

Jones (1978) recognized two subspecies in Aster falcatum Lindl. including multiple synonyms,  Nesom (2004) treated these as varieties within S. falcatum, and Semple in Semple et al. 2002 treated the two taxa as subspecies in S. falcatum.  Brouillet et al. (2006 FNA) treated them as varieties:

• var. falcatum (Plants cespitose, 1–5(–10)-stemmed, usually sparsely appressed-strigose, with cormoid caudices; new shoots developing near the bases of old stems; peduncles long, slender, bracts 1–5; phyllaries subequal (outer longest and foliaceous), apices not strongly squarrose)
• var. communtatum (Torr. & A. Gray) G.L. Nesom (Plants colonial, usually densely hairy, rhizomes entangled, usually 1-stemmed, sometimes clumped; new shoots developing at ends of elongated rhizomes; peduncles stout, bracts 2–10+; phyllaries ± unequal, apices strongly squarrose)