Plants of the Ranunculus genus, Buttercups, are herbaceus perennials and annuals, consisting of about 400 species worldwide, found mostly in temperate and cold regions and on tropical mountains. Most of the species are land-based, but several grow in shallow, standing water. Stems are hair-covered or naked, erect to trailing, branching or simple, sometimes floating in water. Some species with trailing stems are rooting at the nodes.
Leaves are alternate or mostly basal or entirely basal. The basal leaves are usually long-stalked and stem leaves often short-stalked or stalkless. Leaf shapes are simple or more often palmately compound to finely dissected, often variable on the same individual.
Flowers grow from buds on the stem tops, usually showy on long stalks, single or several on branches. Sepals are usually 5, greenish, deciduous. Petals are usually 5, sometimes more or less, yellow or white, often fading to whitish with age, bearing a minute nectary pit covered by a scale toward the base. The flowers have 10 to many stamens, pistils are usually numerous.
The fruits, called achenes, are very small and grow many in a hemispheric or cylindric head in the center of the flower. The achenes are usually tipped with a small spine or hook, called a beak. Species are often identified by the shape and size of the beak.
All buttercups contain toxic glycosides. In large quantities, these compounds will cause salivation, as well as inflammation of the mouth and abdominal pains with convulsions usually proceeding death. As an example, the juice of the leaves of the common Field Buttercup (R. acris) is poisonous, and may cause blisters on sensitive skin, but has been used as an application to remove warts.