Machaeranthera canescens, hoary aster

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Intermountain Flora
Biennial or short-lived perennial (in var. leucanthemifolia sometimes apparently winter-annual), 1-5 dm tall, or in more robust forms up to 1 m, subsimple to freely or even diffusely branched, with 1-several stems from the base; herbage usually finely canescent-puberulent, sometimes also sstipitate-glandular, especially in the inflorescence, varying to seldom wholly glabrous; leaves saliently toothed, the teeth and apex spinulose-tipped, varying to sometimes entire; basal leaves linear-oblanceolate to spatulate or subrotund, up to 10 cm long (including the petiole) and 1 or even 2 cm wide, often deciduous before anthesis, the cauline ones smaller, often linear; heads several to more or less numerous, terminating the branches, the disk mostly 6-15 (20) mm wide; involucre (5.5) 6-10 (12) mm high, canescent-puberulent or glandular or both, its bracts well imbricate in (3) 4-8 series, all appressed to more often many or most of them evidently squarrose-tipped, with a relatively short green tip, that of the middle ones usually evidently shorter than the chartaceous base, some of the bracts sometimes somewhat anthocyanic; rays mostly 8-25 (or more in vars. ambigua and incana), bright bluish-purple, 5-15 mm long, pistillate and fertile, or the ray-flowers very rarely wanting; style-appendages equaling or longer than the stigmatic portion; achenes 3-4 mm long, thinly hairy (or glabrous in var. ambigua); 2n = 8.

Cronquist, A., Holmgren, A.H., Holmgren, N.H., Reveal, J.L., and Holmgren, P.K. (1994) "Intermountain Flora" pg.266, vol. 5, The New York Botanical Garden New York.