This is the least common of the three field buttercups. It grows scattered throughout the lowlands, especially in coastal areas. It prefers a dry lime-rich and nutrient-poor soil and is intolerant to trampling. It can sometimes be found on sand dunes near the sea.
The plant is recognisable by its grooved and hairy flower-stalks, and down-turned sepals – unique amongst the Ranunculus varieties, but mainly the bulbous stem base, or corm, from which it derives its name and which grows just beneath the soil line. After the summer flowers die back the corms survive the winter beneath the soil.
This variety is not as tall as the meadow or creeping buttercup, growing to a height of only 40cm at most.
As with other varieties of buttercup the leaves are divided into 3 deep-lobed leaflets, with the middle leaflet advancing from the others on its own small stalk.
The flowers are a rich even yellow colour with 5 petals. The sepals, as well as folding downwards as the flower opens, are also covered in a mass of tiny white hairs.
Like other varieties it contains the toxic substance, glycoside ranunculin when fresh, but if dried the toxin dissipates. Livestock avoid it because of its deleterious effects on the digestive system.