1. Arctanthemum arcticum (Linnaeus) Tzvelev in A. I. Tolmatchew, Fl. Arct. URSS. 10: 115. 1987.
Chrysanthemum arcticum Linnaeus, Sp. Pl. 2: 889. 1753; Dendranthema arctica (Linnaeus) Tzvelev; Leucanthemum arcticum (Linnaeus) de Candolle
Perennials, forming tufts of 1–10+ rosettes; rhizomes at or below ground, fleshy, tough, branched; taproots (young plants) 3–6(–10) mm diam. Stems glabrous or sparsely woolly proximally to ± densely white-woolly near heads. Leaves sometimes glaucous; petioles 0–95 mm; bases cuneate to truncate, sheathing to clasping (distal), margins revolute, teeth obtuse to rounded, sometimes mucronulate, faces glabrous or sparsely woolly, glabrescent; basal and proximal cauline blades ± fan-shaped to cuneate or spatulate, 6–50 × 4–35 mm, lobes usually 3–7, apices blunt; distal blades linear, 4–35 × 1–28(–40) mm, bases attenuate, margins crenate, dentate, or entire, apices acute or obtuse; faces ± woolly, glabrescent. Peduncles usually bracteate, bracts 0–4, linear-lanceolate to linear, 6–19 mm. Ray laminae 8–12 mm. Disc corollas: tubes greenish yellow, (1.1–)1.4–2 mm, throats and lobes yellow turning brownish, throats 0.7–1 mm, sometimes very sparsely glandular, lobes (0.25–)0.4–0.6 mm. Cypselae 1.5–2.5 mm. 2n = 18 (72?).
Subspecies 2 (2 in the flora): coastal Alaska and low-arctic Canada, arctic Eurasia, ne Asia (s to Japan).
When Hultén described Chrysanthemum arcticum subsp. polare, he mapped the two subspecies. Along the Bering Strait in Alaska, all the material appears to belong to subsp. polare, except at Norton Bay, where a specimen (ALA) could be attributed to subsp. arcticum. That population would be very disjunct from the range of the subspecies along the south coast of Alaska. The two subspecies do not overlap widely in North America.