- Name also: Sulfur Cinquefoil, Rough-fruited Cinquefoil, Erect Cinquefoil
- Family: Rose Family – Rosaceae
- Growing form: Perennial herb.
- Height: 30–60 cm (12–25 in.). Stem erect, sturdy, upper part branched, densely haired, upper part also with glandular hairs.
- Flower: Corolla regular (actinomorphic), yellow–almost white (sulphur-coloured), approx. 1.5–2.5 cm (0.6–1 in.) broad; petals 5, usually shallowly notched, 6–12 mm (0.25–0.5 in.) long, slightly longer than calyx. Calyx 5-lobed; with epicalyx. Stamens 30. Gynoecium separate, pistils many. Inflorescence a dense corymb.
- Leaves: Alternate, basal leaves long-stemmed, stem leaves short-stemmed–stalkless, stipulate. Lowest leaves with 5–7 leaflets, upper leaves with 3 leaflets. Leaflets lanceolate–virtually linear, with toothed margin until base, margins and underside sparsely haired, green. Stipules entire–lobed. No flowerless leaf rosettes.
- Fruit: Receptacle bears several quite round, light brown, glossy, matt achenes.
- Habitat: Fields, meadows, banks, roadsides, waste ground, harbours, loading areas.
- Flowering time: June–August.
Finland’s flora is not stable and unchanging, but is rather subject to constant change. In the last ten thousand years since the Ice Age Finland’s vegetation has developed from aromatic tundra vegetation through the Warm Period when the land was dominated by broad-leaved forests until the current pine forests and bogs that prevail throughout the country. The fastest and most violent changes have however occurred in the last 50 years due to human activity.
Human activity has confined many wild plants to smaller areas, but it also brings a constant stream of new plants to the country. Some of these also manage to establish themselves here, but usually only in places affected by human activity. There are no shortage of aliens in Finland: of the approximately 1400 vascular plants that are known in Finland, almost half have arrived with people, many of them hundreds and thousands of years ago.
Until the 1940s sulphur cinquefoil was a very rare casual alien in Finland, but for one reason or another it has become much more common in a short space of time. In the north it grows as far as Kuopio, but there are far more observations made in the south-west. Sulphur cinquefoil has also shown signs of becoming established, surviving in some of the same places for several years. The sharp growth in the number of sulphur cinquefoil observations is partly due to more intense botanic research, but the whole phenomenon is difficult to explain. The species probably came to Finland mixed in with crop seed, especially clover seed. Finnish sulphur cinquefoils have travelled from central Europe, and partly from Russia too. Sulphur cinquefoil is a very impressive plant: its sturdy stem can be almost one metre (3.3 feet) high and its flowers are larger than those of Finland’s other cinquefoils. It is no wonder that the species is also a popular ornamental.