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Potentilla
See list of 19 species in this genusPhylogenetic study by Erikkson et al. (1998) showed that an inclusive Potentilla is non-monophyletic and also showed that Duchesnea is nested within it. Therefore, several segregate genera are recognized here ( Argentina, Comarum, Dasiphora, and Sibbaldiopsis), and Duchesnea is subsumed under Potentilla. Reference: Rydberg (1898).
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1a. Bractlets definitely larger than the sepals, with 3 conspicous teeth at the apex; receptacle enlarged in fruit, somewhat resembling a “strawberry”, but rather dry and insipid tasting
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1b. Bractlets of ± similar size as the sepals or smaller, lacking conspicuous apical teeth (though the margins may have small teeth); receptacle not enlarged and remaining dry
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2a. Flowers solitary on axillary peduncles [Fig. 847]; stems slender, herbaceous, prostrate and trailing (though often ascending at anthesis), rooting at some nodes and/or the apex (usually erect to ascending and not rooting in P. erecta); style slender, not thickened near the middle or base (conical at base and thickned near apex in P. erecta and P. reptans, both very rare introductions)
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3a. Stems erect to ascending, though sometimes procumbent at anthesis, not rooting at the nodes; stem leaves sessile or subsessile; basal rosette ephemeral, usually absent at anthesis
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3b. Stems prostrate (though initially ascending), rooting at some nodes and/or the apex; stem leaves petiolate (sometimes sessile or subsessile in P. simplex); basal rosettes persisting through anthesis
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4a. Many or all of the flowers with 4 sepals and petals; leaf blades glabrous or glabrate; upper leaves with 3 or 4 leaflets; bractlets lanceolate; stipules narrow-ovate
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4b. Flowers with 5 sepals and petals; leaf blades pubescent on the abaxial surface (+/- glabrous in P. reptans); upper leaves with usually 5 leaflets; bractlets linear-lanceolate; stipules lanceolate
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5a. Petals (6–) 8–12 mm long; anthers (1–) 1.3–2 mm long; epicalyx segments lanceolate to oblong or elliptic; stems from a slender root
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5b. Petals 4–7 (–10) mm long; anthers 0.6–1 mm long; epicalyx segments linear to narrow-lanceolate; stems from a thickened rhizome
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6a. Flowers from the axil of the first well-developed cauline leaf [Fig. 847]; terminal leaflet usually less than 2 times as long as wide; plants shorter, 5–15 cm at anthesis; rhizome 5–20 mm ×4–8 mm
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6b. Flowers usually from the axil of the second well-developed cauline leaf; terminal leaflet usually more than 2 times as long as wide; plants taller, 20–40 cm at anthesis; rhizome 20–80 ×5–20 mm
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2b. Flowers usually few to many in a terminal cyme (the flowers rarely solitary); stems erect to spreading or sometimes prostrate, but not trailing and rooting (trailing and rooting with woody stems in P. verna), the inflorescence usually with bracts; style thickened near the middle or base
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7a. Leaf blades sparsely to densely tomentose on the abaxial surface (long, straight or merely curved hairs also present in some species, especially P. inclinata and P. intermedia)
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8a. Styles (1–) 1.5–2.5 (–3) mm long, short-conic near the base and then filiform and prolonged, the longer ones 2–3 times as long as the mature ovary; petals 4–10 (–11) mm long; filaments 1.5–3.5 mm long; anthers 0.7–1.2 (–1.6) mm long
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9a. Leaflets sparsely tomentose abaxially, toothed with elongate, triangular-lanceolate teeth mostly 5–15 mm long, the sinuses between the teeth usually extending ⅓ to ½ the distance to the midrib
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9b. Leaflets densely tomentose abaxially, crenate to crenate-serrate with teeth mostly 2–5 mm long, the sinuses between the teeth usually extending less than ⅓ the distance to the midrib
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8b. Styles 0.6–1.2 mm long, conic or columnar, shorter than to slightly longer than the mature ovary; petals (2.5–) 4–7 mm long; filaments 0.8–1.5 (–2.5) mm long; anthers 0.3–0.6 (–1.2) mm long
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10a. Lower leaves with 5–7 leaflets, these pinnately arranged or the upper 3 confluent and appearing subpalmately arranged [Fig. 848]; styles glandular at the base
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10b. Lower leaves with 4–7 leaflets, these definitely palmately arranged when numbering 5 or more, styles not glandular at the base (though sometimes papillose)
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11a. Leaflets revolute, each with 2–4 (–6) tooth-like lobes, densely silver-tomentose abaxially; basal leaves much larger than the middle stem leaves; style base papillose
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11b. Leaflets with plane or scarcely revolute margins, coarsely serrate to pinnatifid with (3–) 4–10 (–12) teeth or lobes, sparsely to moderately gray-tomentose abaxially; basal leaves relatively similar in size and outline to the middle stem leaves; style base epapillose
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12a. Leaflets pale green abaxially; petals 4–5 (–5.7) mm long; segments of epicalyx oblong-ovate to oblong, obtuse to acute at the apex (in part)
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12b. Leaflets usually gray-green abaxially; petals 5–7 mm long; segments of epicalyx narrow-lanceolate to lanceolate, acute at the apex
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7b. Leaf blades glabrous or pubescent with straight or merely curved hairs on the abaxial surface
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13a. Lower leaves with 3 leaflets
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14a. Plants cespitose or mat-forming, the flowering stems 1–10 (–20) cm tall
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15a. Dwarf, cespitose plants without procumbent woody stems, 1–4 cm tall; stipules ovate, blunt to abruptly pointed at the apex; leaflets 5–13 mm long
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15b. Mat-forming plants with numerous, procumbent woody stems that root at the nodes, the flowering stems up to 10 (–20) cm tall; stipules linear to narrow-lanceolate, sharply pointed at the apex; leaflets (5–) 8–35 (–40) mm long (in part)
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14b. Plants simple to branched, but neither cespitose nor mat-forming, the flowering stems (10–) 20–120 cm tall
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16a. Androecium with 15–20 stamens bearing anthers 0.3–0.5 mm long; stems hirsute; petals 2–5 mm long, slightly shorter than to subequal in length to the sepals; achenes green-brown to brown, striate-ribbed
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13b. Lower leaves with (4–) 5–9 leaflets [Fig. 849]
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17a. Petals white; leaflets with a few teeth near the apex; achenes smooth
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17b. Petals yellow; leaflets with teeth or tooth-like lobes extending from the apex to at least below the middle of the leaflet and often nearly or quite to the base of the leaflet; achenes striate-ribbed or smooth in P. rivalis
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18a. Mat-forming plants with numerous procumbent woody stems that root at the nodes, the flowering stems 3–10 (–20) cm tall; style slightly dilated near apex (in part)
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18b. Simple or branched, erect to spreading plants, without procumbent, rooting stems, the flowering stems (–15) 25–80 cm tall; style slender at apex
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19b. Androecium with 15–30 stamens bearing anthers 0.6–1.2 (–1.5) mm long; petals subequal to or longer than the sepals; achenes usually striate-ribbed
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20a. Petals 4–5 (–5.7) mm long, slightly shorter to slightly longer than the sepals; stems without glandular hairs, often tomentose (at least above, varying to nearly glabrous) (in part)
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20b. Petals (6–) 7–12 mm long, slightly to evidently longer than the sepals; stems usually with glandular hairs (in addition to longer, eglandular ones), lacking tomentum
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21a. Stems arising centrally from a withered rosette of leaves (i.e., primary leaves borne on the stem); anthers 0.8–1.2 (–1.5) mm long; stipules lobed; achenes 1.2–1.8 mm long
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21b. Stems arising laterally to a persistent basal rosette of leaves (i.e., primary leaves basal); anthers 0.7–0.9 mm long; stipules entire; achenes 1–1.2 mm long
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Each photo represents one species in this genus.