Potentilla plattensis
Potentilla pensylvanica
Platte cinquefoil, Platte River cinquefoil
Norwegian cinquefoil, Pennsylvania cinquefoil, pennsylvanian cinquefoil, potentille de pennsylvanie, prairie cinquefoil
initially decumbent to sometimes ascending, becoming prostrate or supported by vegetation, (0.3–)0.5–3.5(–4.5) dm, lengths 1.5–2.5(–4) times basal leaves.
ascending to erect, (0.3–)1–4(–6) dm.
pinnate with distal leaflets ± distinct, 2–15(–20) × 1–3 cm;
petiole 0.5–5 cm, straight hairs common, tightly appressed, 0.5(–1) mm, stiff, cottony hairs absent, glands absent or sparse;
primary lateral leaflets (3–)4–6(–8) per side, on distal (1/4–)1/2–3/4 of leaf axis, overlapping to separate, largest ones obovate, 0.5–1.5(–2) × 0.5–1(–1.3) cm, distal (1/2–)2/3 to whole margin pinnately incised 3/4+ to midvein, ultimate teeth 5–10, linear-oblanceolate, 1.5–8(–10) × 1–2 mm, apical tufts less than 0.5 mm, surfaces green to grayish green, not glaucous, straight hairs sparse to common (sparser adaxially), tightly appressed, 0.5 mm, stiff, cottony hairs absent, glands absent or inconspicuous.
pinnate, (2–)4–20(–25) cm;
petiole 1–8 cm, long hairs sparse to abundant, rarely absent, spreading to ascending, 0.5–3 mm, weak to ± stiff, short hairs abundant to dense, rarely absent, cottony or crisped hairs absent, glands sparse to abundant, often obscured;
leaflets (2–)3–5(–7) per side, on distal 1/2–3/5 of leaf axis, separate to scarcely overlapping, terminal ones narrowly to broadly oblanceolate, (1–)1.5–5(–6) × 0.5–1.5(–2) cm, margins strongly revolute, incised ± 3/4 to midvein, sometimes more or only ± 1/2, undivided medial blade 2–4(–8) mm wide, teeth 4–8(–10) per side, triangular-ovate to linear-elliptic, surfaces usually ± dissimilar, abaxial ± grayish to nearly white, rarely green, long hairs sparse to abundant (mostly on veins), rarely absent, 0.5–1.5 mm, ± weak, short hairs usually abundant to dense, rarely absent, crisped and cottony hairs absent, glands ± abundant, sometimes obscured, adaxial green to gray-green, long hairs sparse to abundant, rarely absent, spreading to ascending, ± 1 mm, short hairs ± abundant, sometimes obscured, rarely absent, cottony and crisped hairs absent, glands ± abundant.
1–3.
1–4.
(1–)3–15(–20)-flowered, loosely cymose, sometimes racemiform.
(1–)3–40-flowered, congested or elongating in fruit.
1–4(–5) cm, ± recurved in fruit.
0.2–1 cm (proximal to 3.5 cm).
epicalyx bractlets narrowly elliptic to linear-lanceolate, 2–5(–6) × 0.5–2 mm;
hypanthium 3–4 mm diam.;
sepals 3–6 mm, apex acute;
petals 4–7 × 3–6 mm;
filaments 1–2.5 mm, anthers 0.5–1 mm, usually ± 1/2 as long as filaments;
carpels 10–20, styles 1.5–2.5 mm.
epicalyx bractlets usually ± lanceolate-elliptic, rarely ± ovate-elliptic, 3–6(–8) × (1–)1.5–2(–2.5) mm, lengths ± equal to sepals, margins ± revolute;
hypanthium 3–6 mm diam.;
sepals (3–)4–6(–8) mm, apex acute to obtuse, abaxial surfaces: venation indistinct, glands abundant, ± evident;
petals pale to bright yellow, (3–)4–7 × (3–)4–7 mm, lengths ± equal to sepals;
filaments (0.5–)1–2 mm, anthers 0.5–0.8(–1) mm;
carpels 50–100, styles papillate-swollen in proximal ± 1/2, ± 1 mm.
(1.3–)1.5–1.9 mm, smooth, often ± carunculate.
1.2 mm, ± to strongly rugose.
= 70.
= 28.
Potentilla plattensis
Potentilla pensylvanica
Potentilla plattensis occurs mostly east of the Continental Divide from the Canadian Prairies to the mountains of New Mexico. The species barely enters Idaho at Monida Pass (Clark County). Populations also exist in the White Mountains of east-central Arizona and the mountains of southern Utah. The species is relatively uniform throughout its range but there is often significant seasonal variation, such that plants can be compact and densely strigose in early summer but elongate and subglabrous later in the season.
Where the ranges of Potentilla plattensis and P. ovina overlap, the two are sometimes difficult to distinguish. The habitats are usually distinct, in that P. plattensis generally occurs in moist valley bottoms and P. ovina occurs in rocky uplands. Differences in vestiture are also diagnostic: hairs of P. plattensis are 0.5 mm and tightly appressed; those of P. ovina are longer and looser.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Even in the reduced circumscription used here, Potentilla pensylvanica is exceptionally widespread, occurring in North America from Alaska to Hudson Bay, in the Great Plains and the North American Cordillera to northern Mexico. The species also grows across Siberia (where it has sometimes been called P. sibirica) and as isolated occurrences in the southwestern Alps and Spain (J. Soják 1987c; A. Kurtto et al. in J. Jalas et al. 1972+, vol. 13). One place P. pensylvanica does not occur is in Pennsylvania; the epithet was applied by Linnaeus to cultivated plants originating from Canada. Collections from Quebec are probably introductions (J. Cayouette, pers. comm.). The Oregon citation of P. pensylvanica (D. Mansfield 2000) refers to P. jepsonii.
Significant variation occurs within Potentilla pensylvanica, especially regarding vestiture and plant stature. J. Soják (1987c) has described several varieties, all Eurasian except var. brevipila (long hairs 0.6–1 mm); diminutive specimens from the Brooks Range of northern Alaska, isolated from other known populations of P. pensylvanica, have been described as P. brooksensis. Although much of the ecogeographic variation may merit recognition, at least at varietal level, doing so is postponed pending further analysis and clarification of nomenclature. Among the extremes are plants from the Great Plains, which have abundant long silky hairs overlying and obscuring the velvety layer of short hairs (resembling sympatric P. litoralis), and glabrate (except for glands) populations in Alaska. E. Hultén (1968) erroneously referred to the latter as P. pensylvanica var. glabrata (Lehmann) S. Watson; that name is a synonym of P. ovina var. ovina (sect. Multijugae). Most populations in Alaska also have larger than average flowers (petals to 7 × 7 mm, anthers ca. 1 mm).
Although Potentilla pensylvanica var. strigosa Pursh has been one of the most commonly used varieties in North America, the name has been effectively lectotypified by J. Soják (1987c) on a collection from Siberia. Soják identified this collection as the hybrid between P. pensylvanica and the Asian P. sanguisorba D. F. K. Schlechtendal; var. strigosa accordingly does not occur in North America.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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