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scarlet cinquefoil, Thurber's cinquefoil

silkyleaf cinquefoil, silkyleaf or giant or southern Rocky Mountain cinquefoil

Stems

(2–)3–7(–10) dm.

(2–)3–7(–8) dm, lengths (1–)1.5–2.5 times basal leaves.

Basal leaves

palmate, (2–)4–15(–30) cm;

petiole (2–)3–10(–25) cm, long hairs sparse to common, spreading, 1–3.5 mm, weak, glands sparse to abundant, sometimes absent;

leaflets 5(–7), at tip of leaf axis, central one (1–)2–6(–8) × (0.5–)1–2.5(–4) cm, petiolules 0(–10) mm, distal 3/4 to whole margin incised 1/5–1/4 to midvein, teeth (4–)7–15(–19) per side (sometimes secondarily toothed), (1–)2–3(–5) mm, teeth apex acute to ± obtuse, surfaces slightly to strongly dissimilar, abaxial pale green to white, straight hairs sparse to abundant, often dense on veins, 0.5–3 mm, cottony hairs absent or sparse to dense, glands ± sparse or absent, sometimes obscured, adaxial green, straight hairs sparse to abundant, 0.2–1 mm, cottony hairs absent, glands ± sparse or absent.

pinnate, 15–45(–50) cm;

petiole (5–)8–20 cm, long hairs abundant to dense, ascending to appressed, (1–)2–3 mm, ± stiff, rarely weak, short or crisped hairs absent or sparse, cottony hairs absent, glands sparse, often obscured;

leaflets not conduplicate, lateral ones evenly paired, (3–)4–7 per side on distal ± 1/2 of leaf axis, most pairs ± decurrent, rachis winged, distal sometimes confluent with terminal leaflet, larger leaflets narrowly obovate, (2–)3–7 × 1–2.5 cm, distal 3/4+ of margin incised 1/3 to midvein, teeth 6–18 per side, 1–4 mm, surfaces ± similar, abaxial grayish, long hairs sparse to common (mostly on veins), 0.5–2 mm, ± stiff, rarely weak, short-crisped hairs absent or sparse to common, cottony hairs absent, glands sparse to common, adaxial green to grayish, long and short hairs not differentiated, sparse to common, crisped and cottony hairs absent, glands absent or sparse.

Cauline leaves

stipules usually toothed, sometimes entire.

(0–)1–3.

Inflorescences

(4–)10–35-flowered.

(10–)20–60-flowered.

Pedicels

0.5–4 cm.

(0.5–)1–3(–6) cm.

Flowers

epicalyx bractlets narrowly to broadly lanceolate-elliptic (rarely toothed or lobed), 4–9(–14) × (1–)1.5–2 mm;

sepals 4–10(–15) mm, apex acute to acuminate;

petals ± dark reddish throughout, (3.5–)6–10 × 6–10 mm;

filaments 1.5–3 mm, anthers 0.8–1 mm;

carpels 30–70, styles 2.5–3.5 mm.

epicalyx bractlets lanceolate to narrowly ovate or elliptic, 3–6 × 1–1.5 mm, 2/3 as long as to nearly equal to sepals, abaxial vestiture ± similar to sepals, not glabrescent, straight hairs sparse to common, crisped or cottony hairs usually absent;

hypanthium 3–6 mm diam.;

sepals 4–7 mm, apex acute to acuminate;

petals (6–)7–10 × 5–9 mm;

filaments (1–)1.5–4 mm, anthers 0.7–0.9(–1) mm;

carpels 20–30, styles (1–)1.8–3 mm.

Achenes

1.5 mm, ± rugose.

1.4–1.6 mm, smooth.

2n

= 82.

Potentilla thurberi

Potentilla ambigens

Phenology Flowering summer.
Habitat Dry meadows and adjacent slopes, in conifer woodlands
Elevation 2000–2700 m (6600–8900 ft)
Distribution
from FNA
AZ; NM; nw Mexico
[WildflowerSearch map]
[BONAP county map]
from FNA
CO; NM; WY
[BONAP county map]
Discussion

Varieties 2 (2 in the flora).

The abaxially white-cottony leaflets of var. atrorubens usually make it easily distinguished from var. thurberi, which lacks cottony hairs and is usually less hairy in general. The two varieties sometimes occur together and intermediates between the extremes are common.

The degree of glandularity and the lengths of the central leaflets are greater in the southern populations of both varieties. The glands are less widely distributed on the plants northward and are fewer in northern Arizona and New Mexico. Leaflets are shorter and broader north of Graham County, Arizona, and Otero County, New Mexico.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Of conservation concern.

Potentilla ambigens is one of the more distinctive species in sect. Leucophyllae, comprising exceptionally large plants with large, coarsely hairy leaves. Although sometimes confused with P. hippiana, P. ambigens lacks the crisped-cottony vestiture of that species and is usually morphologically distinctive even where both species occur together (D. G. Anderson, www.fs.fed.us/r2/projects/scp/assessments/potentillaambigens.pdf).

Potentilla ambigens occurs in Wyoming (at least historically), along the eastern slope of the Rocky Mountains to northern Colorado, and in scattered locations in the high mountains of New Mexico as far south as the Sacramento Mountains, Otero County. The species is of conservation concern in Colorado and has not been documented in Wyoming since 1900 (D. G. Anderson, www.fs.fed.us/r2/projects/scp/assessments/potentillaambigens.pdf).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Key
1. Leaflets pale green abaxially, cottony hairs absent.
var. thurberi
1. Leaflets ± white to white abaxially, cottony hairs sparse to dense.
var. atrorubens
Source FNA vol. 9, p. 149. FNA vol. 9, p. 164.
Parent taxa Rosaceae > subfam. Rosoideae > tribe Potentilleae > Potentilla > sect. Rubrae Rosaceae > subfam. Rosoideae > tribe Potentilleae > Potentilla > sect. Leucophyllae
Sibling taxa
P. albiflora, P. ambigens, P. anachoretica, P. angelliae, P. anglica, P. anserina, P. arenosa, P. argentea, P. arizonica, P. basaltica, P. bicrenata, P. biennis, P. biflora, P. bimundorum, P. bipinnatifida, P. brevifolia, P. breweri, P. bruceae, P. brunnescens, P. canadensis, P. concinna, P. cottamii, P. crantzii, P. crebridens, P. crinita, P. cristae, P. demotica, P. drummondii, P. effusa, P. elegans, P. erecta, P. flabellifolia, P. fragiformis, P. furcata, P. glaucophylla, P. gracilis, P. grayi, P. hickmanii, P. hippiana, P. holmgrenii, P. hookeriana, P. hyparctica, P. inclinata, P. intermedia, P. jepsonii, P. johnstonii, P. lasiodonta, P. litoralis, P. macounii, P. millefolia, P. modesta, P. morefieldii, P. multijuga, P. multisecta, P. nana, P. newberryi, P. nivea, P. norvegica, P. ovina, P. paucijuga, P. pedersenii, P. pensylvanica, P. plattensis, P. pseudosericea, P. pulchella, P. pulcherrima, P. recta, P. reptans, P. rhyolitica, P. rimicola, P. rivalis, P. robbinsiana, P. rubella, P. rubricaulis, P. sanguinea, P. saximontana, P. sierrae-blancae, P. simplex, P. sterilis, P. stipularis, P. subgorodkovii, P. subjuga, P. subvahliana, P. subviscosa, P. supina, P. thuringiaca, P. tikhomirovii, P. townsendii, P. uliginosa, P. uschakovii, P. vahliana, P. verna, P. versicolor, P. villosa, P. villosula, P. vulcanicola, P. wheeleri
P. albiflora, P. anachoretica, P. angelliae, P. anglica, P. anserina, P. arenosa, P. argentea, P. arizonica, P. basaltica, P. bicrenata, P. biennis, P. biflora, P. bimundorum, P. bipinnatifida, P. brevifolia, P. breweri, P. bruceae, P. brunnescens, P. canadensis, P. concinna, P. cottamii, P. crantzii, P. crebridens, P. crinita, P. cristae, P. demotica, P. drummondii, P. effusa, P. elegans, P. erecta, P. flabellifolia, P. fragiformis, P. furcata, P. glaucophylla, P. gracilis, P. grayi, P. hickmanii, P. hippiana, P. holmgrenii, P. hookeriana, P. hyparctica, P. inclinata, P. intermedia, P. jepsonii, P. johnstonii, P. lasiodonta, P. litoralis, P. macounii, P. millefolia, P. modesta, P. morefieldii, P. multijuga, P. multisecta, P. nana, P. newberryi, P. nivea, P. norvegica, P. ovina, P. paucijuga, P. pedersenii, P. pensylvanica, P. plattensis, P. pseudosericea, P. pulchella, P. pulcherrima, P. recta, P. reptans, P. rhyolitica, P. rimicola, P. rivalis, P. robbinsiana, P. rubella, P. rubricaulis, P. sanguinea, P. saximontana, P. sierrae-blancae, P. simplex, P. sterilis, P. stipularis, P. subgorodkovii, P. subjuga, P. subvahliana, P. subviscosa, P. supina, P. thurberi, P. thuringiaca, P. tikhomirovii, P. townsendii, P. uliginosa, P. uschakovii, P. vahliana, P. verna, P. versicolor, P. villosa, P. villosula, P. vulcanicola, P. wheeleri
Subordinate taxa
P. thurberi var. atrorubens, P. thurberi var. thurberi
Name authority A. Gray: Pl. Nov. Thurb., 318. (1854) Greene: Erythea 1: 5. (1893)
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