Ranunculus is a large genus of about 400 species of plants in the Ranunculaceae. It includes the buttercups, spearworts, water crowfoots and the lesser celandine (but not the greater celandine of the poppy family Papaveraceae).
They are mostly herbaceous perennials with bright yellow or white flowers (if white, still with a yellow centre); some are annuals or biennials. A few have orange or red flowers and occasionally, as in R. auricomus, petals may be absent.
The Water crowfoots (Ranunculus subgenus Batrachium), which grow in still or running water, are sometimes treated in a separate genus Batrachium. They have two different leaf types, thread-like leaves underwater and broader floating leaves although for some species, such as R. aquatilis, a third, intermediate leaf form occurs.
Buttercups usually flower in April or May but flowers may be found throughout the summer especially where the plants are growing as opportunistic colonisers, as in the case of garden weeds.
All Ranunculus species are poisonous when eaten fresh by cattle, horses, and other livestock, but their acrid taste and the blistering of the mouth caused by their poison means they are usually left uneaten. Poisoning can occur where buttercups are abundant in overgrazed fields where little other edible plant growth is left, and the animals eat them out of desperation. Symptoms include bloody diarrhea, excessive salivation, colic, and severe blistering of the mucous membranes and gastrointestinal tract. When Ranunculus plants are handled, naturally occurring ranunculin is broken down to form protoanemonin, which is known to cause contact dermatitis in humans and care should therefore be exercised in excessive handling of the plants. The toxins are degraded by drying, so hay containing dried buttercups is safe.
Ranunculus species are used as food plants by the larvae of some Lepidoptera species including Hebrew Character and Small Angle Shades.
Some species are popular ornamental flowers in horticulture, with many cultivars selected for large and brightly coloured flowers.
An old superstition says that if you hold a buttercup under your face, and yellow light is reflected on your face, it means that you like butter.
In the interior of the Pacific Northwest of the United States the buttercup is called ‘Coyote’s eyes’ — iceyéeyenm sílu in Nez Perce and spilyaynmí áčaš in Sahaptin. In the legend Coyote was tossing his eyes up in the air and catching them again when Eagle snatched them. Unable to see, Coyote made eyes from the buttercup.
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