Potentilla subjuga
Potentilla arenosa
Colorado cinquefoil
thick, not columnar, not sheathed with marcescent whole leaves.
(0.8–)1–2.5(–3.5) dm.
ascending to erect, (0.3–)0.8–2.5(–4.5) dm, lengths (2–)3–5 times basal leaves.
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.
1.5–12(–20) cm;
petiole 1–7(–15) cm, long hairs sparse to abundant, spreading to ± ascending, rarely loosely appressed, 1–2(–2.5) mm, usually stiff, sometimes weak (subsp. chamissonis), verrucose, short and/or crisped hairs absent or sparse to abundant, cottony hairs absent, glands absent or sparse;
leaflets separate to ± overlapping, central obovate, 1–3.5(–4.5) × 0.5–2(–3) cm, usually petiolulate, petiolule to 5 mm, base cuneate, margins slightly revolute, distal ± 3/4 incised ± 1/2 to midvein, teeth (2–)3–4(–6) per side, ± approximate to distant, surfaces dissimilar, often strongly so, abaxial white to gray, long hairs 0.5–1.8 mm, cottony-crisped hairs ± dense, adaxial green, sometimes grayish green, long hairs sparse to abundant, short-crisped hairs sparse to abundant.
1–3.
(0–)1–2.
3–20(–30)-flowered.
1–7(–15)-flowered.
0.5–2 cm (proximal to 3 cm).
1.5–5 cm in flower, to 6(–10) cm in fruit.
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.
epicalyx bractlets linear-lanceolate to lanceolate-elliptic, 2–5(–7) × 0.4–1.2(–1.5) mm, 1/4–1/2 as wide as sepals, margins usually flat, red glands absent or sparse and inconspicuous;
hypanthium 3–5 mm diam.;
sepals 3–6(–8) mm, apex acute;
petals 4–7(–10) × 4–7(–9) mm, ± longer than sepals;
filaments 0.8–1 mm, anthers 0.4 mm;
carpels 28–40, apical hairs absent, styles conic-columnar, strongly papillate-swollen in proximal 1/5–1/3, 1–1.5 mm.
1.2–1.6 mm.
1.1 mm.
Potentilla subjuga
Potentilla arenosa
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.)
Subspecies 2 (2 in the flora).
The name Potentilla arenosa is now used for most arctic and subarctic plants previously treated as P. hookeriana or P. nivea subsp. hookeriana (Lehmann) Hiitonen. As noted by J. Soják (1986), the type of P. hookeriana has quinate leaves; that name is now restricted to a Rocky Mountain species in sect. Rubricaules. The arctic and subarctic material was briefly (1989–1999) called P. nivea, as discussed under that species. Because the type of P. nivea var. arenosa and other northern Asian specimens correspond closely to the North American plants, the name P. arenosa is assigned here.
The two subspecies differ only in one character, the petiole hairs, but are largely allopatric. Subspecies arenosa occurs in western and northern Greenland, northern North America (very northern in the east), and northern Asia (and perhaps northeasternmost European Russia); subsp. chamissonis occurs in southern Greenland, northeastern North America (more southern than subsp. arenosa), and northern Europe at least east to the Urals.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Petioles with common to abundant short and/or stiff crisped hairs in addition to long verrucose hairs. | subsp. arenosa |
1. Petioles with sparse or no short and/or soft crisped hairs in addition to long verrucose hairs. | subsp. chamissonis |
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