Achillea nobilis

Perennials, (10-)15-60 cm (taprooted). Stems 1(-4), erect, simple, glabrous or sparsely tomentose. Leaves sessile; blades ovate, 1.5-3 cm × 10-15 mm, 1-2-pinnately lobed, (bases auriculate, slightly clasping) faces ± hairy. Heads 30-100+, in simple or compound, corymbiform arrays. Phyllaries 10-13+ in (1-)2 series, (midribs light green) oblong (apices papillose, translucent), abaxial faces glabrous. Receptacles flat to slightly convex; paleae narrowly oblong, 2-2.5 mm. Ray florets 8-10(-13), pistillate, fertile; corollas white, laminae 1-1.5 × 2-2.5 mm. Disc florets 10-25+; corollas grayish white, 1.5-2.5 mm. Cypselae 0.75-1 mm. 2n = 18, 27.

Flowering mid Jul-early Sep. Pastures, disturbed roadsides; 900-1500 m; introduced; Mont.; Europe.

Achillea nobilis was introduced in the flora area through cultivation. It has been reported in Minnesota, Massachusetts, and New York; herbarium sheets indicate that those reports were based on cultivated specimens. It was first collected in Montana in 1902; it appears to have become established in that state, where it is known from Lake and Flathead counties.