Potentilla plattensis
Potentilla brunnescens
Platte cinquefoil, Platte River cinquefoil
brownish cinquefoil, slender brown cinquefoil, slender cinquefoil
conspicuous, usually golden.
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 nearly erect, (1.5–)3–7 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.
sometimes 2-ranked, palmate, (5–)10–30 cm;
petiole (1.5–)5–25(–50) cm, long hairs sparse to abundant, appressed to spreading, 1–2 mm, ± stiff, short, crisped, and cottony hairs absent, glands ± abundant;
leaflets (5–)7–9, at tip of leaf axis, separate to slightly overlapping, largest ones oblanceolate-elliptic to narrowly obovate, (2–)5–10 × 1–4 cm, margins flat to ± revolute, distal 3/4 to nearly whole length ± evenly incised (1/4–)1/2–3/4+ to midvein, undivided medial blade 2–15(–20) mm wide, teeth (5–)7–10 per side, linear to broadly lanceolate, 3–15 mm, surfaces ± similar, abaxial paler, green, not glaucous, long hairs sparse to common, short-crisped hairs absent or sparse, cottony hairs absent, glands ± abundant.
1–3.
1–3(–4).
(1–)3–15(–20)-flowered, loosely cymose, sometimes racemiform.
12–30(–70)-flowered.
1–4(–5) cm, ± recurved in fruit.
0.2–1(–4) 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 lanceolate to elliptic, 3–6 × 1–2 mm, hairs sparse to common, loosely appressed to spreading, glands common to abundant;
hypanthium 4–6(–8) mm diam.;
sepals 4–8(–9) mm, apex acute to acuminate;
petals 6–9 × 6–10 mm;
filaments 1–2 mm, anthers 0.6–1 mm;
carpels 30–60, styles filiform-tapered, papillate-swollen proximally, 1.5–2 mm.
(1.3–)1.5–1.9 mm, smooth, often ± carunculate.
1.5 mm.
= 70.
Potentilla plattensis
Potentilla brunnescens
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 conspicuous golden glands, dark green color, and relatively broad leaflets make Potentilla brunnescens one of the better-defined species of sect. Graciles, though it has often been treated as a variety of P. gracilis. The glands, which are often on septate stalks, are particularly conspicuous on the epicalyx bractlets, hypanthium, and sepals, and at the junction of petiole and leaflets. The species occurs from the Blue Mountains of Oregon and Washington to western Montana, northern Utah, and north-central Colorado; collections from Alaska are probably not native.
As presented here, Potentilla brunnescens encompasses two morphological extremes that might merit varietal status. Leaflets of the more common and widespread extreme are incised about halfway to the midvein; in contrast, some populations in western Wyoming and adjacent Idaho have leaflets incised 3/4 or more to the midvein. The latter have often been assigned to P. gracilis var. elmeri while reserving P. gracilis var. brunnescens for the former; this is untenable because the type of P. brunnescens is the latter form.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
OR
Flora NW
PNW Herbaria
SW CO Wildflowers
WildflowerSearch
iNaturalist
USDA Plants Database
BC
