- Name also: Common Silverweed, Silverweed Cinquefoil
- Latin synonym: Potentilla anserina
- Family: Rose Family – Rosaceae
- Growing form: Perennial herb. Rhizomatous.
- Height: 5–15 cm (2–6 in.). Stem limp, with runners, rooting, up to 30–80 cm (12–32 in.) long.
- Flower: Corolla regular (actinomorphic), yellow, 2–3 cm (0.8–0.12 in.) broad; petals five, 8–12 mm (0.32–0.48 in.) long, approx. twice as long as calyx. Calyx 5-lobed; epicalyx lobes serrated (ssp. anserina) or entire (ssp. egedii). Stamens 20. Gynoecium separate, pistils over 20. Flowers solitary in axils.
- Leaves: In basal rosette and alternate or opposite on stem, all stalked, stipulate. Blade pinnate, 7–12 pairs (ssp. anserina) or 3–6 pairs (ssp. groenlandica), with terminal leaflet. Leaflets elliptic, with toothed margins, at least underside (sometimes also top) densely white-haired (ssp. anserina) or glabrous–sparsely haired, fleshy (ssp. groenlandica). Stipules long, membranous, brown.
- Fruit: Quite round, brown achene, many together.
- Habitat: Yards, paths, lawns, parks, fields, roadsides, wasteland, boat harbours, also natural seashores.
- Flowering time: June–August.
The scientific name that the plant received in Linné’s time (Anser) refers to the greylag goose, which was also the root of the plant’s colloquial name in Finnish. Silverweed has adapted to its habitat among gaggles of geese: it grows in cracks in the rocks, keeping it safe from predatory beaks. Nowadays in many books silverweed has been separated from genus Potentilla and placed in a genus of its own, Argentina, most obviously on account of its doubly lobed leaves.
Silverweed was originally a seashore plant, but most Finnish stands grow in places that have been created by people along roadsides, in flat yards and on park lawns. In southern Finland stands usually appear as tens or even hundreds or metres-long silverweed belts along highways. Silverweed can stand a lot of trampling and lawnmowers because its limp leaves and runners lie on the ground under the blades. It has been planted in yards for its large yellow flowers. At least the form that is silver-haired on both sides of the leaves is a very impressive ornamental.
Silverweed’s Finnish habitat stretches from the sea to the tip of the Gulf of Finland, and inland as far north as Oulu. It is divided into two subspecies, which are quite difficult to tell apart: ssp. anserina has a lot (7–12 pairs) of small-toothed leaflets which are hairy at least on the underside and sometimes on top. The species’ arctic seashore variety ssp. groenlandica has less leaflets (3–6 pairs), and they are quite large and blunt-toothed, sparsely haired or glabrous, and slightly fleshy. Hybrids between the subspecies also grow in the wild as intermediate forms of their parent plants. Silverweed must usually be cross-pollinated to ensure seed production, usually by honey bees and bumblebees. It also spreads efficiently through its runners.