Potentilla plattensis
Potentilla hyparctica
Platte cinquefoil, Platte River cinquefoil
arctic cinquefoil, subarctic 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, 0.2–2(–2.5) dm, lengths 1–3(–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.
not in ranks, ternate, (1–)2–8(–10) cm;
stipules: apex ± acute;
petiole 1–6.5(–8.5) cm, long hairs sparse to common, spreading to subappressed, 0.8–2 mm, weak to ± stiff, glands sparse to common;
leaflets 3, central obovate to broadly obovate, 0.5–2.5(–2.8) × 0.3–2(–2.2) cm, petiolule 0–3 mm, margins flat or slightly revolute, not lobed, distal 1/2–2/3(–3/4) evenly incised ± 1/2 to midvein, teeth (2–)3–5 per side, surfaces ± similar, abaxial usually pale green, sometimes grayish, hairs sparse to abundant, 0.5–1.7 mm, adaxial darker green, hairs and glands sparse.
1–3.
(1–)3–15(–20)-flowered, loosely cymose, sometimes racemiform.
1–3(–5)-flowered.
1–4(–5) cm, ± recurved in fruit.
straight, 0.3–3 cm in flower, to 9 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 narrowly to broadly oblong or ovate, 3.5–7 × 1.5–5 mm, margins flat;
hypanthium 4–7 mm diam.;
sepals 4–8 mm, apex subacute to rounded;
petals pale or bright yellow, 4–9 × 4–6 mm;
filaments 0.5–1.1 mm, anthers 0.2–0.4 mm;
carpels 50–80, styles ± columnar, not or scarcely papillate-swollen proximally, 0.6–0.9 mm.
(1.3–)1.5–1.9 mm, smooth, often ± carunculate.
1.1–1.3 mm.
= 70.
Potentilla plattensis
Potentilla hyparctica
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.)
Subspecies 3 (2 in the flora).
Southern arctic and subarctic plants differ from the northern arctic ones in presumably independent features. Where the two forms are sympatric (western Greenland, northern Quebec, Baffin Island), they appear to remain distinct even in mixed populations and are accordingly treated as subspecies.
Although some features of scattered plants in Alaska and Yukon approach subsp. nivicola Jurtzev & V. V. Petrovsky (described from northeastern Asia), such plants do not otherwise correspond fully with this taxon. Possible hybrids between Potentilla hyparctica and P. pulchella (sect. Pensylvanicae) are addressed in the discussion of sect. Pensylvanicae. Presumed hybrids with P. villosa from the Aleutian Islands, characterized by the combination of basally thickened styles and lack of cottony hairs on leaflet abaxial surfaces, have been named P. ×aleutica Soják.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Epicalyx bractlets narrowly to ± oblong or ovate, 1.5–2 mm wide; central leaflets: petiolules 0–2 mm, bases cuneate. | subsp. hyparctica |
1. Epicalyx bractlets broadly oblong or ovate, 2–5 mm wide; central leaflets: petiolules (0–)2–3(–5) mm, bases broadly cuneate to rounded. | subsp. elatior |
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