Potentilla sect. Rubrae
Potentilla thurberi
scarlet cinquefoil, Thurber's cinquefoil
ascending to nearly erect, not flagelliform, not rooting at nodes, lateral to persistent basal rosettes, (2–)3–7(–10) dm, lengths (2–)3–5 times basal leaves.
(2–)3–7(–10) dm.
basal not 2-ranked;
cauline 1–3;
primary leaves palmate to ± subpalmate, (2–)4–15(–30) cm;
petiole: long hairs spreading to weakly appressed, weak to ± stiff, glands sparse to abundant, rarely absent;
leaflets 5–7, on tip or less than distal 1/10 of leaf axis, ± overlapping or not, oblanceolate or oblong to elliptic or obovate, margins flat, distal 1/2 to whole length evenly incised 1/5–1/4 or less to midvein, teeth (0–)4–15(–19) per side, surfaces similar or slightly to strongly dissimilar, abaxial green to white, cottony hairs absent or sparse to dense, adaxial green, not glaucous, long hairs weak to stiff.
palmate, (2–)4–15(–30) cm;
petiole (2–)3–10(–25) cm, long hairs sparse to common, spreading, 1–3.5 mm, weak, glands sparse to abundant, sometimes absent;
leaflets 5(–7), at tip of leaf axis, central one (1–)2–6(–8) × (0.5–)1–2.5(–4) cm, petiolules 0(–10) mm, distal 3/4 to whole margin incised 1/5–1/4 to midvein, teeth (4–)7–15(–19) per side (sometimes secondarily toothed), (1–)2–3(–5) mm, teeth apex acute to ± obtuse, surfaces slightly to strongly dissimilar, abaxial pale green to white, straight hairs sparse to abundant, often dense on veins, 0.5–3 mm, cottony hairs absent or sparse to dense, glands ± sparse or absent, sometimes obscured, adaxial green, straight hairs sparse to abundant, 0.2–1 mm, cottony hairs absent, glands ± sparse or absent.
stipules usually toothed, sometimes entire.
(4–)10–40(–70)-flowered, cymose, open.
(4–)10–35-flowered.
straight in fruit, 0.3–4 cm, proximal ± longer than distal.
0.5–4 cm.
5-merous;
hypanthium 4–6 mm diam.;
petals dark reddish to reddish orange, ± obcordate, (3.5–)5–10 mm, equal to or longer than sepals, apex retuse;
stamens 20–30;
styles subapical, tapered-filiform, papillate-swollen in proximal 1/5, 2–3.5 mm or less.
epicalyx bractlets narrowly to broadly lanceolate-elliptic (rarely toothed or lobed), 4–9(–14) × (1–)1.5–2 mm;
sepals 4–10(–15) mm, apex acute to acuminate;
petals ± dark reddish throughout, (3.5–)6–10 × 6–10 mm;
filaments 1.5–3 mm, anthers 0.8–1 mm;
carpels 30–70, styles 2.5–3.5 mm.
± rugose.
1.5 mm, ± rugose.
Potentilla sect. Rubrae
Potentilla thurberi
Species 9 (2 in the flora).
Red petals distinguish species of sect. Rubrae from the remaining species assigned here to Potentilla. Most species in the section occur in Mexico. As traditionally defined, sect. Rubrae also includes the southeastern Asian species P. atrosanguinea Loddiges, G. Loddiges & W. Loddiges (3 leaflets), P. argyrophylla Wallich ex Lehmann (3 leaflets), and P. nepalensis Hooker (5 leaflets). The first is available in the horticultural trade and was reported in a strawberry field in New Brunswick, Canada (B. Boivin 1966b; H. J. Scoggan 1978–1979, part 3); it did not become naturalized. The name P. argyrophylla var. atrosanguinea (Loddiges, G. Loddiges & W. Loddiges) Hooker f., used in the Flora of China (Li C.-L. et al. 2003c) is incorrect; P. argyophylla (1831) is a name later than P. atrosanguinea (1823).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (2 in the flora).
The abaxially white-cottony leaflets of var. atrorubens usually make it easily distinguished from var. thurberi, which lacks cottony hairs and is usually less hairy in general. The two varieties sometimes occur together and intermediates between the extremes are common.
The degree of glandularity and the lengths of the central leaflets are greater in the southern populations of both varieties. The glands are less widely distributed on the plants northward and are fewer in northern Arizona and New Mexico. Leaflets are shorter and broader north of Graham County, Arizona, and Otero County, New Mexico.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Basal leaves palmate; leaflets 5(–7), distal 3/4 to whole margin incised, surfaces slightly to strongly dissimilar; petals ± dark reddish throughout; cauline leaves: stipules usually toothed, sometimes entire; widespread, Arizona, New Mexico. | P. thurberi |
1. Basal leaves usually ± subpalmate, sometimes palmate; leaflets (5–)7, distal 1/2–3/4 (sometimes nearly whole) margin incised, surfaces ± similar; petals dark reddish proximally, reddish orange distally; cauline leaves: stipules usually entire; Coconino County, Arizona. | P. sanguinea |
1. Leaflets pale green abaxially, cottony hairs absent. | var. thurberi |
1. Leaflets ± white to white abaxially, cottony hairs sparse to dense. | var. atrorubens |
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