6. Rhodiola Linnaeus, Sp. Pl. 2: 1035. 1753; Gen. Pl. ed. 5, 457. 1754.
Roseroot [Greek rhodon, rose, alluding to odor of rootstock in R. rosea] Roseroot [Greek rhodon, rose, alluding to odor of rootstock in R. rosea]
Reid V. Moran
Herbs, perennial (dying back in winter to rootstock), not viviparous, 0.3-6 dm, glabrous [pubescent]. Stems a rootstock with apex mostly above ground, erect, spreading, or decumbent, commonly branching to form clumps, fleshy, with brown scalelike [or green] leaves; flowering stems from axils of brown scale-leaves on stout rootstock partly above ground. Leaves persistent, cauline, alternate, sessile, subclasping basally; blade elliptic to ovate or oblanceolate to linear, obovate, or oblong, laminar (mostly to 1 mm thick), 0.5-5.5 cm, somewhat fleshy, base not spurred, margins entire or toothed; veins not conspicuous. Inflorescences cymose or spikelike to subcapitate. Flowers bisexual or unisexual, erect, 4-6-merous; sepals connate basally, all alike (unequal in R. rosea); petals erect or spreading, distinct, greenish, white, rose, dark red, or yellowish; calyx and corolla not circumscissile in fruit; nectaries quadrate to linear; stamens 2 times as many as sepals, epipetalous; filaments mostly adnate to corolla at base; pistils erect, nearly distinct; ovary base straight; styles 2+ times shorter than ovary. Fruits erect. Seeds oblanceoloid or pyriform, ribbed, finely cross-ribbed.
Species ca. 40 (3 in the flora): North America, Eurasia; montane to arctic areas.
In Rhodiola, inflorescences are borne in axils of scale leaves on the rootstocks, which are partly above ground. They are thinner and leafier than those of Hylotelephium. This treatment largely follows R. T. Clausen (1975), except that he made Rhodiola a subgenus of Sedum.