Potentilla nana
Potentilla effusa
arctic cinquefoil, dwarf cinquefoil
branch cinquefoil
ascending to erect, 0.1–0.5(–0.7) dm, lengths 1–2 times basal leaves.
(0.5–)1.5–4(–5.5) dm, lengths 2–3(–4) times basal leaves.
not in ranks, ternate, 1–5 cm;
stipules: apex acute;
petiole 0.5–3.5 cm, long hairs sparse to abundant, ascending to spreading, 0.5–2 mm, ± soft, glands sparse to common;
leaflets 3, central obovate, 0.5–2 × 0.5–1 cm, petiolule 0–1 mm, margins revolute, not lobed, distal 1/2–2/3 evenly incised ± 1/2 to midvein, teeth 3–4(–6) per side, surfaces ± similar, green (paler abaxially), hairs sparse to abundant, 0.8–1.2 mm, glands sparse to common.
pinnate, (3–)5–15(–25) cm;
petiole 0.5–5(–8) cm, long hairs absent to abundant, ± appressed, 1–3 mm, stiff to weak, short and crisped hairs absent or obscured, cottony hairs abundant (at least on first-formed leaves), glands sparse or obscured;
leaflets not conduplicate, lateral ones evenly to unevenly paired, 2–5(–7) per side (secondary leaflets sometimes interspersed) on distal 1/3–1/2 of leaf axis, distal pairs usually not decurrent or confluent with terminal leaflet, larger leaflets oblanceolate to narrowly obovate, 1–2.5(–3) × 0.3–1.3(–1.8) cm, distal (1/2–)2/3–3/4 (rarely more) of margin incised ± 1/2 to midvein, teeth (1–)2–9 per side, 1–4 mm, surfaces similar, gray to white or ± green, abaxial: long hairs sparse to common (at least on veins), 0.5–1.5 mm, weak to stiff, short or crisped hairs absent or sparse, sometimes obscured, cottony hairs absent or sparse to dense, glands absent, sparse, or obscured, adaxial: long hairs absent or sparse to common, short or crisped hairs absent or sparse, cottony hairs absent or sparse to abundant, glands absent or sparse.
2–6+.
1(–2)-flowered.
7–30-flowered.
straight, 0.2–1.5 cm in flower, to 5 cm in fruit.
0.3–3 cm.
epicalyx bractlets oblong or ovate, 2.5–5 × 1.5–3.5 mm, margins revolute;
hypanthium 3–3.5 mm diam.;
sepals 2.5–5 mm, apex ± acute;
petals pale yellow, 4–8 × 4–6 mm;
filaments 1.2–2 mm, anthers 0.3–0.4 mm;
carpels 40–50, styles ± columnar, not or scarcely papillate-swollen proximally, 0.8–1.2 mm.
epicalyx bractlets linear to narrowly lanceolate, 1–2.5(–3) × 0.3–1 mm, 1/2–2/3 as long as sepals, abaxial vestiture often much sparser than sepals, often glabrate or glabrescent distally, straight hairs absent or sparse, cottony hairs usually abundant (at least proximally), sometimes absent or nearly so (var. rupincola);
hypanthium 2–6 mm diam.;
sepals 3–6(–7) mm, apex long acuminate;
petals 4–6.5 × 4–6 mm;
filaments 1–3.5 mm, anthers 0.5–1 mm;
carpels 3–15, styles 1.5–2.1 mm.
1.4–1.6 mm.
1.8–2.1 mm, smooth.
Potentilla nana
Potentilla effusa
Potentilla nana has most often been considered a race of P. hyparctica or as the priority name for P. hyparctica. As now defined, P. nana occurs in an arc across southern Alaska, from the Aleutian and Pribilof islands to the Alaskan panhandle and adjacent British Columbia. T. Wolf (1908) treated it as a dwarf form of P. fragiformis; J. Soják (1996) interpreted P. nana as a hybrid species originating from cross(es) between P. fragiformis and P. hyparctica. Although the hybrid hypothesis has morphologic support, P. nana has a unique combination of morphologic features and has a distinct range from both P. fragiformis and P. hyparctica. The species are also ecologically segregated: P. nana is a coastal heath and gravel slope species, like P. hyparctica; P. fragiformis is strictly maritime coastal.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Varieties 2 (2 in the flora).
In the southern Rocky Mountains, Potentilla effusa is relatively distinct from P. hippiana both morphologically and geographically, with P. effusa mostly east of the Continental Divide and P. hippiana mostly west. In general, P. hippiana differs from P. effusa in having leaflets more evenly paired, more tightly serrate with teeth often occurring on the whole margin, and more bicolored with abaxial vestiture of crisped rather than cottony hairs. Stems of P. effusa have more cauline leaves on average than P. hippiana, and vestiture of epicalyx bractlets of P. effusa (as here circumscribed) is never sericeous.
The distinction between the two species is marred by intermediate populations throughout their shared range in the northern Rocky Mountains and Great Plains. Most regional floras focused on these areas have accordingly included Potentilla effusa within P. hippiana, sometimes without infraspecific distinction. An alternate solution has been the recognition of P. hippiana subsp. effusa, with the subspecies further subdivided into the two varieties recognized here. The varieties themselves intergrade; P. effusa var. ×coloradensis (Rydberg) Th. Wolf is available for the hybrid.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Leaflets gray to white, surfaces moderately long-hairy and moderately to densely cottony. | var. effusa |
1. Leaflets ± green, surfaces glabrous or sparsely to moderately long-hairy (at least on veins) and not or sparsely cottony. | var. rupincola |
BC
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
MN Wildflowers
