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13. Rhodiola Linnaeus, Sp. Pl. 2: 1035. 1753.

红景天属 hong jing tian shu

Rhodiola crenulata

Credit: Harvard University Herbaria

Chamaerhodiola Nakai; Clementsia Rose.

Herbs perennial, with some dimorphism. Rhizome a fleshy caudex, thick or slender, apex usually at or slightly above ground level. Caudex leaves present, usually reduced and scalelike, but sometimes with well-developed leaf blade. Flowering stems 1 to many, arising from axils of caudex leaves, annual, simple, leafy; dried remains of old stems sometimes persisting. Stem leaves usually alternate, occasionally verticillate or opposite, simple, fleshy. Inflorescences terminal, a simply or compoundly corymbiform or dichotomous cyme, less often 1-flowered, rarely a helicoid cyme or with additional axillary inflorescences arising from distal leaf axils, usually bracteate and pedunculate. Flowers usually bisexual, sometimes unisexual (when plants dioecious, or gynodioecious in Rhodiola alsia subsp. alsia and rarely in R. purpureoviridis subsp. phariensis). Calyx (3 or)4- or 5(or 6)-parted. Petals ± free, as many as sepals. Stamens in 2 series, usually 2 × as many as petals; antepetalous stamens adnate to basal part of petals; anthers mostly purple before anthesis, later turning yellow, basifixed or less often dorsifixed, 2-loculed. Nectar scales linear, oblong, suborbicular, or quadrangular. Ovary superior; carpels as many as petals. Follicles few to many seeded.

About 90 species: high altitudes and frigid zone of N hemisphere; 55 species (16 endemic) in China.

Sedum carnegiei Raymond-Hamet (Ann. Carnegie Mus. 8: 418-420. 1913), known only from Xizang (near Lhasa Shi), seems to be a possible member of Rhodiola, based on the turnip-shaped caudex, stem leaves with a basal spur, specialized flowering stem/lateral inflorescence, and deeply divided calyx and corolla. It differs from other members of that genus in its caudex leaves, which are fleshy and lack the persistent, scalelike base characteristic of other members of Rhodiola. The habit is like that of Rosularia. The exact generic placement needs further investigation.

Rhodiola multibracteata H. Chuang (Acta Bot. Yunnan. 19: 225. 1997) has been described from Yunnan. No material has been seen by the present authors, and it has not been possible to place it within the following key. In the protologue, it was compared with R. kirilowii, from which it was said to differ in having narrower leaves, many bracts, hardly unguiculate male flower petals, and erect follicle beaks. Its relationship to that species needs investigation.


1 Caudex leaves (at least inner ones) with a distinct leaf blade, green.   (2)
+ Caudex leaves without a distinct leaf blade, reduced, usually scalelike and not green.   (7)
       
2 (1) Caudex leaves conspicuously dimorphic: outer ones scalelike and membranous, inner ones with a distinct leaf blade.   (3)
+ Caudex leaves monomorphic, all with a green leaf blade (sometimes deciduous but leaving a dark brown, persistent petiole).   (4)
       
3 (2) Caudex leaves prominently basally spurred; stem leaves 3.5-4 × 1-1.3 mm   4 R. handelii
+ Caudex leaves basally spurless; stem leaves 7-14 × 1.3-2.2 mm   5 R. smithii
       
4 (4) Caudex leaves sessile, without persistent, scalelike base; stem leaves with distinct basal spur   Sedum carnegiei (see above)
+ Caudex leaves distinctly petiolate, petiole to 10 mm, turning dark brown and persisting after leaf blade falls; stem leaves (when present) basally spurless.   (5)
       
5 (4) Anthers dorsifixed; inflorescences helicoid-cymose   1 R. hobsonii
+ Anthers basifixed; inflorescences corymbiform, sometimes reduced to a single flower or monochasium.   (6)
       
6 (5) Caudex leaf blade linear-oblanceolate to linear-rhomboid, ca. 1.5 mm wide; petals 2.5-3 mm   2 R. humilis
+ Caudex leaf blade broadly spatulate to obovate, ca. 5 mm wide; petals 5-10 mm   3 R. primuloides
       
7 (1) Inflorescences dense racemes, much longer than wide, with uniformly distributed flowers   8 R. semenovii
+ Inflorescences cymose, sometimes reduced to a single flower, sometimes elongated but then clearly made up of cymes, usually in several discontinuous whorls.   (8)
       
8 (7) Stem leaves 4-6, in a single whorl; plants less than 5 cm tall.   (9)
+ Stem leaves many, alternate, aggregated or subverticillate, if verticillate then plants more than 10 cm tall, less often 6-verticillate.   (10)
       
9 (8) Flowers bisexual; inflorescences 13-18-flowered, bracteate, pedicels 1.5-2.5 mm; stem leaf blade 2-6 × 2.5-4 cm   6 R. prainii
+ Flowers unisexual; inflorescences 1-6-flowered, ebracteate, pedicels 10-13 mm; stem leaf blade 0.8-1.5 × 0.4-0.7 cm   7 R. stapfii
       
10 (8) Old flowering stems persistent; follicles connate in basal 1/2.   (11)
+ Old flowering stems not persistent; follicles almost free.   (34)
       
11 (10) Petals ca. 10 mm, margin entire or sparsely fimbriate   9 R. dumulosa
+ Petals less than 6 mm, margin entire.   (12)
       
12 (11) Remnants of old shoots and stems few; flowers somewhat large.   (13)
+ Remnants of old shoots and stems numerous; flowers small.   (22)
       
13 (12) Part of caudex producing new stems not enlarged each year.   (14)
+ Part of caudex producing new stems somewhat enlarged each year.   (18)
       
14 (13) Caudex 0.5-0.7 cm in diam.; flowering stems 1-5, straight; flowers usually 4-merous.   (15)
+ Caudex 1-1.5 cm in diam.; flowering stems numerous, flabellate; flowers usually 5-merous, rarely 4-merous.   (16)
       
15 (14) Flowering stem leaves linear   24 R. angusta
+ Flowering stem leaves lanceolate, oblong, obovate-rhombic, or broadly obovate   17 R. atuntsuensis
       
16 (14) Petals often red   21 R. fastigiata
+ Petals often yellow, especially when sepals yellow or yellowish green.   (17)
       
17 (16) Stem leaves linear, linear-lanceolate, or lanceolate; stamens usually shorter than petals   22 R. pamiroalaica
+ Stem leaves elliptic; stamens equaling or longer than petals   23 R. litwinowii
       
18 (13) Flowering stems often straw-colored when dry; leaves smooth.   (19)
+ Flowering stems often purplish red or pink when dry; leaves finely and minutely hairy.   (20)
       
19 (18) Plants pubescent   25 R. himalensis
+ Plants glabrous   28 R. tangutica
       
20 (18) Stem leaf margin entire; petals greenish yellow; pedicels densely papillate   27 R. sherriffii
+ Stem leaf margin entire or apically dentate; petals deep purple; pedicels smooth.   (21)
       
21 (20) Stem leaves 1.7-2.7 × 0.4-1 cm   25 R. himalensis
+ Stem leaves 0.8-1.5 × ca. 0.2 cm   26 R. alsia
       
22 (12) Nectar scales linear to broadly so   10 R. gelida
+ Nectar scales suboblong, quadrangular, or suborbicular.   (23)
       
23 (22) Stem leaves elliptic to ovate or ovate-lanceolate.   (24)
+ Stem leaves lanceolate to ovate or oblong-oblanceolate, rarely linear to oblong-linear.   (28)
       
24 (23) Stem leaves shortly petiolate, margin irregularly crenulate   16 R. subopposita
+ Stem leaves sessile, margin entire (coarsely dentate in R. recticaulis).   (25)
       
25 (24) Flowering stems less than 4 cm   17 R. atuntsuensis
+ Flowering stems more than 12 cm.   (26)
       
26 (25) Petals yellow; stem leaf margin coarsely dentate; inflorescences corymbiform-capitate   18 R. recticaulis
+ Petals purplish red or red; stem leaf margin entire, sometimes mammillate; inflorescences cymose.   (27)
       
27 (26) Plants (6-)15-18 cm tall; stem leaves ovate or ovate-lanceolate; flowers often 4-merous   19 R. gannanica
+ Plants to 30 cm tall; stem leaves linear to narrowly ovate; flowers usually 5-merous   20 R. tibetica
       
28 (23) Caudex base not or only slightly enlarged.   (29)
+ Caudex base enlarged.   (31)
       
29 (28) Stems 1-2 mm in diam.   15 R. nobilis
+ Stems 0.5-1 mm in diam.   (30)
       
30 (29) Flowering stems blackening when old; caudex leaves 6-8 mm wide; sepal apex subobtuse to obtuse   12 R. coccinea
+ Flowering stems grayish when old; caudex leaves 3-5 mm wide; sepal apex acute   14 R. kashgarica
       
31 (28) Caudex densely clustered; leaves linear-lanceolate   12 R. coccinea
+ Caudex slightly or not clustered; leaves linear.   (32)
       
32 (31) Caudex less than 1 cm in diam., persistent old flowering stems and branches usually few; flowers often white, 5-merous; inflorescences ca. 1 cm in diam.   13 R. kansuensis
+ Caudex 1-3 cm in diam., persistent old flowering stems and branches usually more than 100; flowers often purplish red, 4-merous; inflorescences 1.2-1.5 cm in diam.   (33)
       
33 (32) Winter bud at apex of rhizome conspicuous; flowering stems 6-9 cm   11 R. quadrifida
+ Winter bud at apex of rhizome absent; flowering stems 1-5 cm   12 R. coccinea
       
34 (10) Flowers usually bisexual.   (35)
+ Flowers usually unisexual (plants hermaphroditic or rarely gynodioecious in R. purpureoviridis subsp. phariensis).   (44)
       
35 (34) Petals apex awnlike, with a mucro to 1 mm   55 R. liciae
+ Petals apex subobtuse.   (36)
       
36 (35) Flowering stems leafy at middle or near apex.   (37)
+ Flowering stems leafy throughout.   (39)
       
37 (36) Flowering stems with leaves in a whorl at middle of stem   54 R. sexifolia
+ Flowering stems with leaves grouped near apex of stem.   (38)
       
38 (37) Stem leaves 1-1.5 cm   52 R. chrysanthemifolia
+ Stem leaves 2-3 cm   53 R. ovatisepala
       
39 (36) Stem leaves 2-4 cm, margin divided.   (40)
+ Stem leaves 1-2.3(-3) cm, margin serrate or dentate.   (41)
       
40 (39) Flowering stems ca. 15 cm; stem leaves elliptic to obovate, 5-7 cm; sepals ca. 3 mm   48 R. sinuata
+ Flowering stems 8-11 cm; stem leaves oblong, 1-3 cm; sepals ca. 6 mm   49 R. tieghemii
       
41 (39) Stem leaf margin with 4 or 5 dentate lobes on each side   50 R. sacra
+ Stem leaf margin with 2 to several shallowly incised serrations on each side.   (42)
       
42 (41) Stem leaves 0.2-0.3 cm wide   42 R. wallichiana
+ Stem leaves 0.4-1.1 cm wide.   (43)
       
43 (42) Stem leaves elliptic, narrowly ovate, or ovate, margin irregularly and remotely serrate, base shallowly cordate; petal margin entire   38 R. purpureoviridis
+ Stem leaves oblong to obovate-oblong, margin with 2 shallowly incised serrations on each side, base attenuate; petal margin apically erose   51 R. alterna
       
44 (34) Carpel beak reflexed.   (45)
+ Carpel beak not reflexed.   (46)
       
45 (44) Sepals 0.5-1 mm; petals spatulate to oblong-lanceolate   46 R. yunnanensis
+ Sepals ca. 3 mm; petals oblong or triangular-ovate   47 R. forrestii
       
46 (44) Carpels ovoid or narrowly so, basally narrowed.   (47)
+ Carpels oblong or narrowly so, basally thickened.   (50)
       
47 (46) Flowers usually bisexual   42 R. wallichiana
+ Flowers unisexual.   (48)
       
48 (47) Carpels ovoid, 9-11 mm; stem leaves obtrullate to linear-lanceolate   45 R. macrocarpa
+ Carpels narrowly ovoid, 7-9 mm; stem leaves narrowly elliptic to lanceolate or oblanceolate, or widely oblanceolate.   (49)
       
49 (48) Caudex 0.5-1 cm in diam.; stem leaves 0.6-0.8 cm wide; stamens equaling or slightly longer than petals   43 R. stephanii
+ Caudex 1-2 cm in diam.; stem leaves 0.3-0.5 cm wide; stamens ca. 1.5 × as long as petals   44 R. pinnatifida
       
50 (46) Carpels oblong, ca. 2 × as long as wide.   (51)
+ Carpels narrowly oblong, over 3 × as long as wide.   (54)
       
51 (50) Plants glandular hairy; flowering stems more than 2 per caudex apex   38 R. purpureoviridis
+ Plants not glandular hairy; flowering stems 1 or 2 per caudex apex.   (52)
       
52 (51) Flowering stems transversely wrinkled, mostly leafless; caudex elongate and rhizomelike, covered by scree so that only inflorescences are visible above ground   41 R. atsaensis
+ Flowering stems smooth or longitudinally ridged, leafy; caudex often erect or almost so, not deeply buried.   (53)
       
53 (52) Caudex subprostrate, ascending, or suberect; stem leaves abaxially ± glaucescent; petals of male flowers 5-6 × 1.2-2 mm, those of female flowers 3-4 × 0.9-1.2 mm   39 R. discolor
+ Caudex erect; stem leaves abaxially not glaucescent; petals of male flowers 2.8-4 × 1.2-1.6 mm, those of female flowers 1.5-3 × 0.5-0.7 mm   40 R. bupleuroides
       
54 (50) Stem leaves linear to oblanceolate, margin entire or remotely dentate.   (55)
+ Stem leaves oblong, elliptic, lanceolate, rhombic-ovate, ovate-triangular, or orbicular-cordate, margin crenulate throughout, apically dentate, or sometimes subentire.   (56)
       
55 (54) Caudex prostrate, 0.2-0.4 cm in diam.; flowering stems 2-12 cm; sepals 3-4.5 mm, apex obtuse   36 R. cretinii
+ Caudex erect, 1.5-2.5 cm in diam.; flowering stems 15-60 cm; sepals 1.5-3 mm, apex acute to acuminate   37 R. kirilowii
       
56 (54) Stem leaves rhombic-ovate to elliptic   29 R. calliantha
+ Stem leaves not as above.   (57)
       
57 (56) Flowering stems not leafy apically; stem leaves short, broadest near base.   (58)
+ Flowering stems leafy apically; stem leaves long, usually broadest in distal 1/2.   (59)
       
58 (57) Leaf base cordate, amplexicaul, apex acute; sepals linear, ca. 7 × 1.3 mm; stamens reddish   34 R. heterodonta
+ Leaf base truncate to subcordate, apex shortly acuminate; sepals triangular-linear, ca. 1.1 × 1.3 mm; stamens yellow   35 R. junggarica
       
59 (57) Flowering stems apically papillate; stem leaf margin serrate   33 R. serrata
+ Flowering stems smooth; stem leaf margin subentire, apically sometimes dentate.   (60)
       
60 (59) Persistent old flowering stems and branches black when dry   32 R. crenulata
+ Persistent old flowering stems and branches not black when dry.   (61)
       
61 (60) Plants 20-30 cm tall; stem leaves elliptic-lanceolate, oblong, or broadly oblong-ovate; sepals ca. 1/3 as long as petals   30 R. rosea
+ Plants 10-15 cm tall; stem leaves oblong-spatulate, oblong-lanceolate, or oblong-rhombic; sepals ca. 1/2 as long as petals   31 R. sachalinensis

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