Potentilla plattensis
Potentilla subvahliana
Platte cinquefoil, Platte River cinquefoil
high arctic cinquefoil
stout, columnar, sheathed with marcescent whole leaves.
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.
erect, 0.2–0.6(–1.1) dm, lengths 2–4 times basal leaves.
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.
0.5–2.5(–3) cm;
petiole 0.3–1.5(–2) cm, long hairs common to abundant, spreading to ascending, 1(–2) mm, ± weak, rarely stiff, smooth, crisped/short-cottony hairs usually absent, sometimes sparse, glands sparse to common;
leaflets separate to slightly overlapping, central obovate, 0.5–1.2(–1.5) × 0.4–0.9(–1) cm, subsessile to short-petiolulate, base cuneate, margins revolute, distal 1/2 incised 1/2–3/4 to midvein, teeth (1–)2–3(–4) per side, ± distant, surfaces ± dissimilar, abaxial grayish or yellowish white, long hairs 0.5–1 mm, cottony-crisped hairs ± dense (often obscured by long hairs), adaxial dark green to greenish gray, long hairs ± abundant, other hairs absent.
1–3.
(0–)1(–2).
(1–)3–15(–20)-flowered, loosely cymose, sometimes racemiform.
1(–2)-flowered.
1–4(–5) cm, ± recurved in fruit.
1–2(–3) cm in flower, to 5.5 cm in fruit.
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 lanceolate to elliptic-ovate, rarely linear, 3–6(–7) × 0.8–2(–2.3) mm, (1/2–)2/3 to nearly as wide as sepals, margins flat or ± revolute, red glands absent;
hypanthium 2.5–4 mm diam.;
sepals 3–5(–6) mm, apex obtuse to subacute;
petals 4–8(–9) × 4–9 mm, longer than sepals;
filaments 1–1.3 mm, anthers 0.3–0.5 mm;
carpels 25–35, apical hairs absent, styles conic-columnar, ± papillate-swollen on less than proximal 1/5, 0.9–1.1 mm.
(1.3–)1.5–1.9 mm, smooth, often ± carunculate.
1.2–1.6 mm.
= 70.
= 28 (Russian Far East).
Potentilla plattensis
Potentilla subvahliana
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 major part of the range assigned to Potentilla vahliana by E. Hultén (1968) belongs to P. subvahliana.
Two morphologic types are present within what is accepted here as Potentilla subvahliana. Plants corresponding to the type of P. subvahliana (Wrangel Island) are widespread throughout northeastern Asia (Chukotka) and arctic North America to northwestern Greenland. Some plants in alpine Alaska, Yukon, and east to Amundsen Gulf, Nunavut, are redder, more densely columnar, and less hairy, with smaller leaves having fewer and narrower lobes, more slender one-flowered stems, narrow and entire bracts, narrower sepals, and much narrower epicalyx bractlets. Potentilla subvahliana is tetraploid, perhaps an allopolyploid, and could consist of lineages from different parental combinations.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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