Potentilla plattensis
Potentilla thuringiaca
Platte cinquefoil, Platte River cinquefoil
European cinquefoil, German cinquefoil, potentille de thuringe
sparse, uncolored, minute.
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.
1.5–5(–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.
4–25(–35) cm;
petiole 2–20(–25) cm, hairs sparse to common, ± spreading, 1–2.5 mm, weak, glands absent or sparse;
leaflets 5–7(–9), central one narrowly to broadly oblanceolate, 1–6(–9) × 0.5–2 cm, distal 2/3–3/4+ of margin incised 1/4–1/3(–1/2) to midvein, teeth (4–)6–10(–13) per side, surfaces ± similar, abaxial green to pale green, hairs sparse to common on primary veins, ascending to spreading, 0.5–1.5 mm, weak, adaxial green, hairs more appressed and shorter.
1–3.
1–3;
stipules fused with less than 1/3 of petiole, free portion longer than fused portion.
(1–)3–15(–20)-flowered, loosely cymose, sometimes racemiform.
5–20-flowered.
1–4(–5) cm, ± recurved in fruit.
1–3 cm (proximalmost to 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 linear to lanceolate, 3–8 × 1–1.5(–2) mm;
hypanthium 3–5 mm diam.;
sepals 3–5 mm, apex ± acute;
petals (5–)8–10 × 4–10 mm;
filaments 0.3–1.5 mm, anthers 0.7–0.9 mm;
carpels 35–50, styles 1.1–1.3 mm.
(1.3–)1.5–1.9 mm, smooth, often ± carunculate.
1–1.2 mm, faintly rugose.
= 70.
= 42, 56 (Eurasia).
Potentilla plattensis
Potentilla thuringiaca
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.)
Potentilla thuringiaca might be mistaken for the more widely established P. intermedia of sect. Terminales. In addition to having flowering stems lateral to persistent basal leaves, P. thuringiaca has much larger petals (mostly 8–10 mm versus 4–5 mm), 5–9 leaflets, and tubercles at the bases of the long, spreading hairs.
To the Quebec records (and subsequent collections) reported by R. Cayouette (1966) is added Block Island, Rhode Island (Fernald et al. 9650, GH).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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