Potentilla anserina
Potentilla bruceae
common silverweed, Pacific cinquefoil, silver weed cinquefoil, silverweed
Bruce's cinquefoil
absent or inconspicuous, uncolored.
ascending to nearly erect, (1–)2–5(–6) dm.
petiole (0.5–)1–15(–25) cm, long hairs absent or sparse to dense, 1.5–3.5 mm;
larger leaflets (0.4–)0.5–5(–7) × (0.2–)0.3–2(–3) cm, surfaces: abaxial with long hairs absent or sparse to abundant, not restricted to veins, 0.5–2(–2.5) mm, cottony-crisped hairs usually dense or usually absent (in subsp. groenlandica), adaxial with long hairs absent or sparse to abundant, cottony-crisped hairs usually absent, sometimes sparse to common (especially subsp. yukonensis).
not in ranks, ± subpalmate to subpinnate (proximal leaflets sometimes doubled, distal leaflets confluent and/or decurrent), (2–)5–20(–28) cm;
petiole (1–)3–15(–20) cm, long hairs abundant, appressed to ascending-spreading, 1–2.5 mm, weak often flattened and twisted, sometimes grading to crisped or cottony hairs, short hairs absent, glands absent or sparse;
leaflets 5–7, on distal 1/10–1/4 of leaf axis, ± overlapping, largest ones usually ± obovate, (1–)1.5–5(–6) × 1–3.5(–4) cm, margins flat, distal 2/3–3/4 evenly to unevenly incised ± 1/2 to midvein (often with additional incisions nearly to midvein), undivided medial blade 4–20 mm wide, teeth (2–)3–6(–8) per side (sometimes secondarily toothed), ± lanceolate, 4–11 mm, surfaces ± similar, abaxial ± lighter and hairier, gray-green to grayish, rarely green, not glaucous, long hairs ± abundant, short-crisped hairs absent or sparse to common, cottony hairs usually absent, glands absent or sparse.
1–2.
5–50-flowered.
0.5–3(–4) cm.
epicalyx bractlets narrowly to broadly ovate-triangular or linear to elliptic, (2–)2.5–7(–8) × (0.3–)0.5–3(–3.5) mm, often 2-fid or dentate;
sepals (3–)3.5–7(–9) mm, apex subacute to acuminate;
petals (4–)5–15(–20) × (2.5–)3–10(–12) mm;
filaments (1–)2.5–3.5(–4.5) mm, anthers 0.7–1.3 mm;
carpels (10–)20–200(–250).
epicalyx bractlets broadly lanceolate to elliptic, 3–6(–7.5) × 1.5–2.5(–3) mm, hairs ± common to abundant, loosely appressed to ascending, glands absent or inconspicuous;
hypanthium 3.5–5.5 mm diam.;
sepals 5–10 mm, apex acute to acuminate;
petals 5–10 × 5–10 mm;
filaments 1–2.5 mm, anthers 0.7–1.2 mm;
carpels 15–30, styles filiform-tapered, papillate-swollen proximally, 2–3 mm.
2 mm.
1.4–1.6 mm.
= 63–73, 79, 87, 98, 129.
Potentilla anserina
Potentilla bruceae
Subspecies 4 or 5 (4 in the flora).
Potentilla anserina is polymorphic in most features, especially in hairiness, but also in size and in degree of dissection of leaflets, epicalyx bractlets, and sepals. While most of the variation described by A. G. Blytt (1906) is taxonomically insignificant, A. Rousi (1965) found support for three northern races: subspp. anserina, egedei, and pacifica. He also suggested that P. yukonensis Hultén might qualify as a separate subspecies. This treatment follows J. Soják (1994) in accepting four northern subspecies of P. anserina, all present in North America.
A. Rousi (1965) demonstrated partial interfertility between the races of Potentilla anserina, which form intermediates in all zones of contact. The distinctness of the four races, in spite of intermediates, is upheld by being partly allopatric and occupying different habitats where they are sympatric. As partly interfertile parapatric entities, they are best treated as subspecies.
The vast majority of chromosome counts are tetraploid. Tetraploid plants (2n = 28) are fully fertile; hexaploids (2n = 42) are largely pollen and seed sterile; pentaploids (2n = 35) are probably occasional hybrids (S. Erlandsson 1942, 1942b; A. Rousi 1965). A. Kurtto et al. (in J. Jalas et al. 1972+, vol. 13) considered numbers above tetraploid level as cases of occasional autopolyploidy.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
As redefined by B. Ertter and D. Mansfield (2007), Potentilla bruceae is characterized by irregularly subpalmate, weakly villose leaves. Such plants form relatively consistent and extensive populations in dry meadows centered near Lake Tahoe in California and Nevada, extending to the central Sierra Nevada and to the Warner Mountains in Oregon. This interpretation differs from that previously suggested by Ertter (1992), in which P. bruceae was interpreted as the catchall category for hybrids between P. breweri (sect. Multijugae) and P. drummondii. All three taxa were accordingly treated as varieties of P. drummondii. D. D. Keck (in J. Clausen et al. 1940) treated P. bruceae as a subspecies of P. drummondii; B. C. Johnston (1980) concluded that its placement as a variety of P. breweri was more justified. The three entities unquestionably intergrade (with the type of P. anomalofolia M. Peck possibly one result), but not beyond what is the norm for facultatively apomictic species of Potentilla.
Chromosome numbers reported by J. Clausen et al. (1940) require verification as this species; the irregular behavior observed in meiotic material suggests that at least some of the individuals were hybrids.
See discussion of 29. Potentilla drummondii regarding leaflet dissection and the inclusion of P. bruceae in sect. Graciles.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Epicalyx bractlets equal to or longer than sepals, often 2-fid or dentate; leaflet surfaces: abaxial with cottony-crisped hairs dense, long hairs common to abundant, on and between veins, adaxial glabrous or sparsely to densely hairy; achenes with dorsal groove; inland and seashore plants | → 2 |
1. Epicalyx bractlets shorter than sepals, usually entire, rarely 2-fid or dentate; leaflet surfaces: abaxial with cottony-crisped hairs absent or sparse to dense, long hairs absent or sparse, on veins, adaxial usually glabrous, rarely sparsely to densely hairy; achenes without dorsal groove; seashore or near-coastal plants | → 3 |
2. Hypanthium patelliform (wider than deep) in fruit; epicalyx bractlets narrowly to broadly ovate-triangular, equal to sepals; most of North America. | subsp. anserina |
2. Hypanthium turbinate (± as deep as wide) in fruit; epicalyx bractlets usually linear to elliptic, longer than sepals, rarely subequal; interior w Canada and Alaska. | subsp. yukonensis |
3. Carpels (20–)50–200(–250); leaves (3–)10–50(–75) cm; leaflets (4–)5–10(–15) per side, abaxial surfaces densely hairy, teeth (4–)6–12(–16) per side, teeth apices acute to acuminate, rarely subacute; flowers 1–2.5(–3.5) cm diam. | subsp. pacifica |
3. Carpels 25–60; leaves (1–)2–10 cm, rarely longer; leaflets 2–4(–5) per side, abaxial surfaces glabrous, sometimes sparsely to densely hairy, teeth 2–6(–10) per side, teeth apices rounded to subacute; flowers 0.8–1.5 cm diam. | subsp. groenlandica |
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