Buttercup, common name for a family of flowering plants and for its representative genus. The family comprises about 58 genera and 1750 species and contains many ornamentals, including adonis, clematis, delphinium, anemone, larkspur, and columbine. Buttercups of the family's representative genus possess shiny, conspicuous, lemon-yellow, cup-shaped flowers. Common species include the tall buttercup and the bulbous buttercup, both widely distributed in pastures and meadows, although the latter is restricted to the eastern United States. Cursed crowfoot and small-flowered buttercup have smaller petals and are less conspicuous. Buttercups, marsh marigold, and some other members of the buttercup family produce a harmless glycoside in their tissues. This compound, however, breaks down spontaneously to form an oily substance, protoanemonin, which is a strong irritant. Buttercups are usually avoided by livestock, but, if eaten, may produce severe irritation of the mouth and digestive system. Drying of the plant causes further spontaneous change, and hay containing buttercups cannot harm grazing livestock.
Plants in the order to which the buttercup family belongs are almost all herbaceous (nonwoody) or climbers and are most abundant in temperate areas of the world. Many species are of ornamental value, a few are common weeds, and some are poisonous to mammals, including humans.
The order is diverse, but several features are shared by many members of the group. Vegetatively, these include the herbaceous trait, alternately arranged leaves that lack stipules (small leaflike appendages at the leaf bases), and the production of alkaloids. Flower parts are usually numerous, spirally arranged, and not fused. Members of the order occupy a wide range of habitats, deserts being the only areas in which they are not well represented. In general, however, the members of the order are adapted to moist-to-wet habitats.
The brightly colored flowers found in most of the order function to attract insects for pollination. The order has two flower types: pollen flowers and nectar flowers.
Five of the eight families included in the order contain only a few species. The largest family after the buttercup, the barberry, with about 650 species, mostly North Temperate, includes the mayapple and several useful ornamentals such as Oregon grape and barberry. The moonseed family contains about 400 species of climbers found throughout the tropics. A kind of curare used as a muscle relaxant is obtained from one of its members.
Scientific classification: Buttercups make up the family Ranunculaceae, of the order Ranunculales. The tall buttercup is classified as Ranunculus acris, the bulbous buttercup as Ranunculus bulbosus, the cursed crowfoot as Ranunculus sceleratus, and the small-flowered buttercup as Ranunculus abortivus.