Potentilla plattensis
Potentilla simplex
Platte cinquefoil, Platte River cinquefoil
common cinquefoil, old-field cinquefoil, old-field five-fingers, potentille simple, simple 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.
initially erect to ascending to 5 dm, then arching above ground-level, becoming prostrate, flagelliform, not branched, rooting at distal nodes, (0.5–)1.5–12 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.
persistent or ephemeral, usually palmate, 3.5–20 cm;
petiole 1–15 cm, long hairs ± abundant, appressed to spreading, (0.5–)1–3 mm, weak to ± stiff, glands absent or sparse, sometimes common;
leaflets 5(–7), central narrowly elliptic to obovate, 1.5–5 × 0.5–2.5 cm, distal 1/2–3/4 of margin incised 1/4–1/3 to midvein, teeth 4–8(–13) per side, surfaces similar to ± dissimilar, abaxial green to silvery white, sparsely to abundantly hairy, adaxial green, glabrate or sparsely to moderately hairy.
1–3.
(0–)1 proximal to 1st flowering node, well expanded at anthesis, usually palmate, 2.5–6(–9) cm;
petiole 0–2(–4) cm;
leaflets (3–)5, often more elongate than those of basal leaves, ± elliptic to oblanceolate, sometimes obovate, 1.5–6(–7.5) × 0.5–2(–3) cm, apex acute to obtuse.
(1–)3–15(–20)-flowered, loosely cymose, sometimes racemiform.
solitary flowers at stolon nodes.
1–4(–5) cm, ± recurved in fruit.
1–5(–8.5) 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.
5(–6)-merous;
epicalyx bractlets linear to narrowly lanceolate, 2–5 × 1–1.5(–2) mm, often larger than sepals (especially in bud);
hypanthium 3–5 mm diam.;
sepals 4–6 mm, apex broadly acute;
petals 4–7 × 3–6 mm, apex rounded to ± retuse;
stamens ca. 20, filaments 0.5–2 mm, anthers 0.6–1 mm;
carpels 20–50, styles 0.8–1.5 mm.
(1.3–)1.5–1.9 mm, smooth, often ± carunculate.
0.9–1.2 mm, faintly rugose.
horizontal, irregularly thickened or moniliform, 1–8 cm.
= 70.
Potentilla plattensis
Potentilla simplex
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.)
The distinction between Potentilla simplex and P. canadensis is subtle, and the former is often misidentified as the latter; additional features to distinguish the two species are provided by M. L. Fernald (1931).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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