Oldfield Aster, Frost Weed, Hairy or Hairy White Oldfield Aster
Symphyotrichum pilosum (Willd.) G. L. Nesom is the common, widely distributed species of subsect. Porteriani occurring through much of the eastern deciduous forest area of eastern North America in open sunny locations with disturbed soils such as old field, roadsides, limestone outcrops and pavements and sand dunes. Chmielewski and Semple (2001) summarized much of the ecology and biology known at the time. The species occurs at two ploidy levels, tetraploid (2n=32) and hexaploid (2n=40) with the occasional interploidy level pentatploid hybrid (2n=40) within var. pilosum and between var. pilosum and var. pringlei. The cytogeography has been studied extensively (Semple 1978; Semple and Chmielewski 1985; Chmielewski and Semple and 1989).
Two varieties were recognized in Brouillet et al. (2006 FNA):
Semple, J.C. 1978. The cytogeography of Aster pilosus (Compositae): Ontario and the adjacent United States. Can. J. Bot. 56: 1274-1279.
Semple, J.C., and J.G. Chmielewski. 1985. The cytogeography of Aster pilosus (Compositae-Astereae). II. Survey of the range, with notes on A. depauperatus, A. parviceps and A. porteri. Rhodora 87: 367-379.
Chmielewski, J.G., and J.C. Semple. 1989. The cytogeography of Aster pilosus var. pilosus in southern Ontario revisited. (Compositae: Astereae). Can. J. Bot. 68: 3517-3519.
Chmielewski, J.G., and J.C. Semple. 2001. The Biology of Canadian weeds. 114. Symphyotrichum pilosum (Willd.) Nesom (Aster pilosus Willd.). Canad. J. Plant Sciences 81: 851-865.
Last updated 29 January 2014 by J.C. Semple
© 2014 J.C. Semple, including all photographs unless otherwise indicated