- Family: Buttercup Family – Ranunculaceae
- Growing form: Perennial herb.
- Height: 10–30 cm (4–12 in.). Stems 1–2, stem erect, long-branched, with tuber at base, lower part hairy, upper part mostly leafless.
- Flower: Corolla regular (actinomorphic), golden–bright yellow, shiny, usually 15–30 mm (0.6–1.2 in.) wide; petals 5, longer than sepals. Sepals 5, recurved, white-haired. Receptacle hairy. Stamens many. Gynoecium separate, with many pistils. Flower solitary, terminating stem, flower-stalk grooved.
- Leaves: Alternate, basal leaves 2–5, long-stalked, stem leaves stalkless. Basal leaf blades roundish–triangular, hairy, with 3 leaflets, central leaflet usually quite long-stalked, leaflets 3-lobed, toothed. Stem leaf leaflets sparsely lobed, uppermost leaves with 3 leaflets, entire.
- Fruit: Elliptic, glabrous achene, edges winged, tip with short, very curved bristle. Several achenes together.
- Habitat: Dry meadows, meadows, grassy rocky outcrops, banks, yards, casually in harbours.
- Flowering time: May–June.
Bulbous buttercup is a demanding plant that grows on the Åland Islands and Finland’s south-western archipelago. It has spread to the mainland around harbours in coastal towns and thrives on dry, sunny, often south-facing meadow ridges. At first glance it resembles meadow buttercup but can be differentiated by the swollen basal part of the stem. The plant’s scientific name bulbosus, ’bulbous’ refers to this construction, although it is slightly misleading: it doesn’t have a bulb but rather a basal tuber. The overwintering tuber’s regenerating bulbil develops a new stem that grows a new tuber every summer. By autumn all the old tuber’s nutrition has been used up and it has slowly rotted and died, but by then the new tuber has reached full size and the plant can overwinter safely. The tuber’s almost vertical stem roots are able to shorten themselves and pull the tuber up to a suitable depth to protect it from the winter cold. Bulbous buttercup cannot propagate itself via its rootstock, and it doesn’t produce runners, so it is completely reliant on its seed production.
Suddenly buttercup species that look like meadow buttercup burst into flower throughout the summer all over the place: bulbous buttercup grows on dry, well-drained land, multiflowered buttercup (R. polyathemoides) favours dryish meadows, meadow buttercup (R. acris) likes a bit damper places, and creeping buttercup (R. repens) likes the wettest environment. Apart from its tuber, bulbous buttercup can be differentiated from its relatives by its sepals, which turn towards the flower-stalk.