Arctanthemum arcticum

(Linnaeus) Tzvelev in A. I. Tolmatchew

in A. I. Tolmatchew, Fl. Arct. URSS 10: 115. 1987

Basionyms: Chrysanthemum arcticum Linnaeus
Synonyms: Dendranthema arctica (Linnaeus) Tzvelev Leucanthemum arcticum (Linnaeus) de Candolle
Treatment appears in FNA Volume 19. Treatment on page 536.
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?).

Distribution

V19-932-distribution-map.gif

Coastal Alaska and low-arctic Canada, arctic Eurasia, ne Asia (s to Japan).

Discussion

Subspecies 2 (2 in the flora).

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.

References

None.

Key

1 Plants 10–40 cm (more in fruit); stems sometimes branched; blades of basal leaves fan-shaped to cuneate or spatulate, 3–5(–7)-lobed; ray laminae (15–)17–25(–31) mm, veins (5–)8–10(–12) Arctanthemum arcticum subsp. arcticum
1 Plants (2.5–)5–20(–26) cm (more in fruit); stems not branched; blades of basal leaves cuneate to spatulate, 0–3-lobed; ray laminae (7–)9–18(–21) mm, veins 4–5(–7) Arctanthemum arcticum subsp. polare