Potentilla sect. Leucophyllae
Potentilla subjuga
Colorado cinquefoil
ascending to erect, not flagelliform, not rooting at nodes, lateral to persistent basal rosettes, (0.3–)1.5–7(–8) dm, lengths (1–)1.5–4(–5) times basal leaves.
(0.8–)1–2.5(–3.5) dm.
basal not 2-ranked;
cauline (0–)1–6+;
primary leaves pinnate to subpinnate (with distal leaflets often confluent), 3–45(–50) cm;
petiole: long hairs usually ± to tightly appressed, sometimes ascending, usually stiff, sometimes weak, glands absent or sparse or obscured;
leaflets (5–)7–15, on distal (1/6–)1/5–2/3 of leaf axis, separate to ± overlapping distally, oblanceolate to narrowly obovate, oblong, or cuneate, margins flat, distal 1/4 to whole length, rarely less, usually ± evenly incised 1/4–1/2 or less to midvein, sometimes entire, teeth (0–)2–18 per side, surfaces similar to strongly dissimilar, abaxial white to ± green, cottony hairs absent or sparse to dense, adaxial green to white, not glaucous, long hairs mostly weak, sometimes 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.
(5–)7–60-flowered, cymose, open.
3–20(–30)-flowered.
straight in fruit, 0.3–3(–6) cm, proximal usually much longer than distal.
0.5–2 cm (proximal to 3 cm).
5-merous;
hypanthium 2–7 mm diam.;
petals yellow, ± obcordate, (3–)4–10 mm, usually longer than sepals, retuse;
stamens 20–25;
styles subapical, tapered-filiform, papillate-swollen in proximal 1/5 or less, (1–)1.5–3 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 to slightly rugose.
1.2–1.6 mm.
Potentilla sect. Leucophyllae
Potentilla subjuga
Species 4 (4 in the flora).
Section Leucophyllae is an apparent radiation of four species in monsoonal regions of the American Southwest, ranging from the Colorado Plateau, Rocky Mountains, and western Great Plains to the prairies of Canada. The plants share features with sect. Graciles but have consistently pinnate leaves, distal leaflets often decurrent, and petioles commonly densely strigose. Plants are often locally abundant in relatively dry forest openings and open grasslands, tending to be more xeric-tolerant than plants of sect. Graciles.
Descriptions and keys focus on the most distinctive expressions, which are blurred by a propensity for the species to hybridize wherever they grow sympatrically. This is counteracted by at least some level of habitat partitioning; for example, Potentilla hippiana tends to occur on deeper soils and P. crinita on rockier slopes than other species in this section.
As a further complication, key diagnostic characters sometimes sort independently in different parts of the relatively large ranges of the species. The prairie expression described as Potentilla argyrea is particularly problematic, undermining the distinction between P. effusa and P. hippiana in the northern part of their ranges. In the southern Rocky Mountains, the two species are relatively distinct on the basis of correlated vestiture and leaflet toothing. In contrast, the prairie expression combines vestiture closer to P. hippiana with leaflet features of P. effusa. Pending further analysis, B. Boivin (1952) and B. C. Johnston (1980) are followed in retaining this variant in P. hippiana, though without formal taxonomic recognition. Inclusion in P. effusa might prove more justified, as done by J. Soják (2006).
Since Potentilla subjuga (sect. Subjugae) and P. ovina (sect. Multijugae) are sometimes identified as members of sect. Leucophyllae, they are included herein and key out in the third and fifth couplets, respectively.
(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: abaxial surfaces white to gray, crisped or cottony hairs abundant to dense | → 2 |
1. Leaflets: abaxial surfaces ± green to grayish or silvery, crisped or cottony hairs usually absent or sparse | → 4 |
2. Epicalyx bractlets: abaxial vestiture often much sparser than that of sepals, often glabrate or glabrescent distally, straight hairs absent or sparse, cottony hairs usually abundant (at least proximally); lateral leaflets evenly to unevenly paired, teeth (1–)4–9 per side on distal (1/2–)2/3–3/4 (rarely more) of margin, surfaces similar, cottony hairs abundant to dense abaxially, abundant adaxially; Alberta to Manitoba, to Colorado, possibly disjunct in nc New Mexico and ne Utah. | P. effusa |
2. Epicalyx bractlets: abaxial vestiture similar to or ± sparser than that of sepals, usually not glabrescent, straight hairs ± abundant, crisped or sometimes ± cottony hairs absent or sparse to abundant; lateral leaflets evenly (to unevenly in argyrea phase) paired, teeth (5–)7–12(–18) per side on distal (2/3–)3/4 to whole margin, surfaces ± to strongly dissimilar, crisped-cottony hairs abundant to dense abaxially, absent or sparse to common adaxially; c Canada to Nevada, Arizona, and New Mexico, introduced farther east | → 3 |
3. Leaflets (2–)3–6(–7) per side, distal pairs ± decurrent, often confluent with terminal leaflet, surfaces ± to strongly dissimilar; 500–3400 m. | P. hippiana |
3. Leaflets 2(–3) per side, distal pairs not decurrent or confluent with terminal leaflet, surfaces strongly dissimilar; 3400–4000 m. | P. subjuga (sect. Subjugae) |
4. Lateral leaflets often unevenly paired, distal pairs usually not decurrent or confluent with terminal leaflet, surfaces ± green; epicalyx bractlets with cottony hairs sometimes abundant (at least proximally) | → 5 |
4. Lateral leaflets evenly paired, distal pairs ± decurrent, often confluent with terminal leaflet, surfaces greenish to silvery or grayish; epicalyx bractlets with cottony hairs usually absent | → 6 |
5. Stems ascending to erect; basal leaves: leaflets 2–3 per side, incised ± 1/2 to midvein, teeth 2–5 per side; cauline leaves 2–6+; cottony hairs often present (at least on epicalyx bractlets); nc Colorado. | P. effusa |
5. Stems prostrate to ascending; basal leaves: leaflets 3–5 per side, incised 1/2–2/3(–3/4) to midvein, teeth (0–)1–2(–3) per side; cauline leaves 1–2; cottony hairs absent; Uinta and middle Rocky mountains, to Nevada and Colorado. | P. ovina (sect. Multijugae) |
6. Basal leaves 15–45(–50) cm; larger leaflets (2–)3–7 cm, not conduplicate, teeth 6–18 per side on distal 3/4+ of margin; se Wyoming, e slope Rocky Mountains of Colorado to Sacramento Mountains, New Mexico. | P. ambigens |
6. Basal leaves 3–15(–20) cm; larger leaflets 1–3(–4) cm, often conduplicate, teeth (0–)1–5(–9) per side on distal 1/4–1/2(–2/3) or less of margin; s Nevada to sw Colorado, n Arizona, and nw New Mexico. | P. crinita |
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