4. Achillea alpina Linnaeus, Sp. Pl. 2: 899. 1753.
Siberian yarrow, achillée de Sibérie
Achillea sibirica Ledebour
Perennials, 50–80 cm (fibrous-rooted and rhizomatous). Stems 1, erect, branched or unbranched distally, sparsely villous to glabrate. Leaves sessile; blades linear-lanceolate to oblong-lanceolate, 5–10 cm × 4–8 mm, (margins serrate to doubly serrate, teeth antrorse) faces sparingly villous or glabrate. Heads 10–25+, in crowded, simple or compound, corymbiform arrays. Phyllaries 20–30 in ± 3 series, (light green, margins light to dark brown, midribs dark green or yellow-green) lanceolate to oblanceolate, faces (abaxial) sparingly tomentose. Receptacles convex; paleae oblong, 3.5–4.5 mm (apices dark, rounded). Ray florets 6–8(–12), pistillate, fertile; corollas white, laminae 1–3 × 2–3 mm. Disc florets 25–30+; corollas grayish or yellowish white, 2–3 mm. Cypselae 2.5 mm. 2n = 36.
Flowering early Jul–early Sep. Meadows, forest edges, roadsides, lakeshores, along streams, moist soils; 100–600 m; Alta., B.C., Man., N.W.T., Ont., Que., Sask., Yukon; Alaska, Minn., N.Dak.; Asia.
Achillea alpina has been reported (as A. sibirica) as occurring in New Jersey and Missouri. Specimens examined from those states were from plants cultivated in botanical gardens; there is no evidence that Achillea alpina has escaped in those states.