Pacific silverweed

Potentilla pacifica Howell, Fl. N.W. Amer., 179. 1898; Argentina occidentalis Rydberg; A. pacifica (Howell) Rydberg; P. anserina var. grandis Torrey & A. Gray; P. egedei Wormskjold ex Hornemann subsp. grandis (Torrey & A. Gray) Hultén; P. egedei subsp. pacifica (Howell) L. A. Sergienko; P. rolandii B. Boivin

Stems glabrous or sparsely hairy. Leaves erect, rarely horizontal or ascending, (3–)10–50(–75) cm; leaflets (4–)5–10(–15) per side, separate, rarely overlapping, teeth (4–)6–12(–16) per side, teeth apex acute to acuminate, rarely subacute, surfaces: abaxial with long hairs absent or sparse, on veins, cottony-crisped hairs dense, adaxial glabrous, rarely sparsely to densely hairy. Flowers 1–2.5(–3.5) cm diam.; epicalyx bractlets narrowly to broadly ovate-triangular, shorter than sepals, entire, rarely 2-fid or dentate; hypanthium patelliform (wider than deep) in fruit; petals not or rarely overlapping, elliptic; carpels (20–)50–200(–250). Achenes without dorsal groove. 2n = 28.

Flowering summer. Salt and brackish marshes, clay and sandy seashores, maritime drift deposits; 0–150 m; B.C., N.B., Nfld. and Labr., N.S., P.E.I., Que.; Alaska, Calif., Conn., Maine, Mass., N.H., N.Y., Oreg., R.I., Wash.

Pacific and Atlantic populations of subsp. pacifica are widely separated geographically but are essentially the same morphologically, except for the high number of achenes in some west coast populations.