Potentilla sect. Subjugae
Potentilla subjuga
Colorado cinquefoil
ascending to nearly erect, not flagelliform, not rooting at nodes, lateral to persistent basal rosettes, (0.2–)0.4–2.5(–3.5) dm, lengths 2–3 times basal leaves.
(0.8–)1–2.5(–3.5) dm.
basal not 2-ranked;
cauline 0–3;
primary leaves palmate with additional lateral pairs to pinnate (with distal leaflets distinct), (1–)1.5–10(–14) cm;
petiole: long hairs spreading to tightly appressed, weak to stiff, glands absent or sparse;
leaflets 5–7(–9), on distal 1/10–1/3(–1/2) of leaf axis, strongly overlapping or not, oblanceolate-oblong to obovate, margins scarcely to ± revolute, ± whole length evenly incised 1/2–3/4 to midvein, teeth 2–9 per side, surfaces ± to strongly dissimilar, abaxial white to grayish green, cottony hairs sparse to dense, adaxial green to grayish, not glaucous, long hairs ± stiff.
usually palmate with additional lateral leaflets, sometimes pinnate, 3–10(–14) cm;
petiole 1.5–5 cm, vestiture seasonally dimorphic, long hairs abundant, spreading on first-formed leaves, tightly appressed to ascending on later-formed leaves, 1–2 mm, ± stiff (especially on later-formed leaves), cottony and crisped hairs usually absent, glands absent or sparse;
leaflets (3–)5 at tip of leaf axis plus 1(–2) additional pair(s) separated from tip by 3–20 mm, on distal 1/10–1/3(–1/2) of leaf axis, largest leaflets oblanceolate-oblong, (0.5–)1.5–2.5(–3) × 0.3–1 cm, ± whole margin incised 1/2–2/3(–3/4) to midvein, teeth (2–)4–9 per side, usually touching to strongly overlapping, sometimes separate, 2–6 mm, surfaces usually strongly dissimilar (less so on first-formed leaves), abaxial usually white, straight hairs ± abundant (mostly on veins), 1–2 mm, cottony or crisped/cottony hairs ± dense (sparser on first-formed leaves), glands absent or obscured, adaxial green (to grayish), straight hairs sparse to common, 0.5–1.5 mm, cottony and crisped hairs absent, glands sparse.
1–3.
(1–)2–20(–30)-flowered, usually cymose, open.
3–20(–30)-flowered.
straight in fruit, 0.5–2(–3) cm, proximal ± longer than distal.
0.5–2 cm (proximal to 3 cm).
5-merous;
hypanthium 3–5 mm diam.;
petals yellow, ± obcordate, 4–8 mm, equal to or longer than sepals, apex retuse;
stamens ca. 20;
styles subapical, filiform to filiform-tapered or filiform-columnar, papillate-swollen in proximal less than 1/5 if at all, 0.8–2 mm.
epicalyx bractlets narrowly to broadly lanceolate, 2–5(–6) × 1–1.5 mm;
sepals 4–7 mm, apex acute to acuminate;
petals 4–8 × 4–8 mm;
filaments (0.5–)1–2 mm, anthers 0.3–0.8 mm;
carpels 15–30, styles filiform to filiform-tapered, ± papillate-swollen in less than proximal 1/5, 1.5–2 mm.
smooth.
1.2–1.6 mm.
Potentilla sect. Subjugae
Potentilla subjuga
Species 2 (2 in the flora).
Section Subjugae is used primarily to accommodate the unique leaf dissection and vestiture of Potentilla subjuga, which commonly has five palmately arranged leaflets and one, sometimes two, additional pairs of lateral leaflets. Sometimes leaves are simply pinnate with only three terminal leaflets, and sufficient intergradation occurs with P. saximontana that it is also included in the section. This circumscription coincides with the initial concept of Rydberg and Nelson and contrasts with that of B. C. Johnston (1980, 1985).
Section Subjugae is restricted to subalpine and alpine habitats in the Rocky Mountains and adjacent ranges of western North America centered in Colorado. Variation within the section is complex and poorly understood, such that the two species treated here represent only the best expressed extremes with existing names. Other named components of uncertain placement include Potentilla lupina Rydberg, P. minutifolia Rydberg, P. rubricaulis var. nana Clements & E. G. Clements, P. rubripes Rydberg [= P. concinna var. rubripes (Rydberg) C. L. Hitchcock], and P. tenerrima Rydberg.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Potentilla subjuga is centered in the high mountains of Colorado and barely enters New Mexico in the Sangre de Cristo Mountains. Collections from Alberta also apparently belong to this species, but all known collections from Wyoming have been identified as different taxa, at least one currently undescribed. At its most distinctive, P. subjuga is easily recognized by its unique leaf division, with five palmate leaflets subtended by an additional pair (or two) of lateral leaflets. Southern populations, however, are more likely to have only three apical leaflets. The leaflets tend to be strongly bicolored with overlapping teeth, in contrast to most sympatric pinnate species. Petiole vestiture is also distinctive in being seasonally dimorphic, with long hairs on first-formed leaves spreading to ascending and those on later formed leaves tightly appressed, as well as more conspicuously verrucose. Unresolved infraspecific variation exists, and field observations suggest that P. subjuga readily hybridizes with sympatric species, creating a swarm of intermediate specimens.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaflets at tip of leaf axis (3–)5; styles 1.5–2 mm; stems (0.8–)1–2.5(–3.5) dm; inflorescences 3–20(–30)-flowered. | P. subjuga |
1. Leaflets at tip of leaf axis 3; styles 0.8–1.5 mm; stems (0.2–)0.4–1(–1.5) dm; inflorescences (1–)2–5(–10)-flowered. | P. saximontana |
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