Ranunculus acris

Ranunculus acris is a species of flowering plant in the family Ranunculaceae, and is one of the more common buttercups across Europe and temperate Eurasia. Common names include meadow buttercup, tall buttercup, common buttercup and giant buttercup.

Ranunculus acris is a herbaceous perennial plant that grows to a height of 30–100 cm (12–39 in), with ungrooved flowing stems bearing glossy yellow flowers about 25 mm across. There are five overlapping petals borne above five green sepals held upwards against the petals, that turn yellow as the flower matures. It has numerous stamens inserted below the ovary. The leaves are compound, with finely cut, hairy, leaflets. Unlike Ranunculus repens, the terminal leaflet is sessile. As with other members of the genus, the numerous seeds are borne as achenes.

The rare autumn buttercup (R. aestivalis) is sometimes treated as a variety of this species.

The juice of the plant is semi-poisonous to livestock, causing blistering.

The plant is native to Eurasia, but has been introduced across much of the world so that it now has a circumpolar distribution. It is a naturalized species and often a weed in parts of North America, but it is probably native in Alaska and Greenland. In New Zealand it is a serious pasture weed costing the dairy industry hundreds of millions of dollars. It has become one of the few pasture weeds that has developed a resistance to herbicides.

R. acris is a species characteristic of grazed or mown neutral grassland communities, tending to occupy areas where drainage conditions are intermediate between those favoured by R. bulbosus in drier soils, and R. repens in wetter soils. Its abundance is said to be an indicator of grassland age and continuity but does not appear to be a good competitor in species-rich communities dominated by tall grasses.

The flower buds begin developing in late summer in the year before flowering. Floral development is promoted by low winter temperatures, and the plant passes the winter in a rosette form with small green leaves that appear to resist the ravages of frost. Reproduction occurs from seeds and short thick rhizomes that can split to form daughter plants

In horticulture the species may be regarded as a troublesome weed, colonising lawns and paths. However, it may be a welcome feature of wildflower meadows. The double-flowered cultivar R. acris 'Flore Pleno' has gained the Royal Horticultural Society's Award of Garden Merit.