Everyone knows what a buttercup looks like don't they? Bold, bright, shiny yellow flowers that grow in fields and in hedgerows. The buttercup or ranunculus family is a bit more complex that than with several variations on a theme.
The celery-leaved buttercup (Ranunculus sceleratus) is one of those variations. It still has yellow flowers but the petals are quite small and the central 'works' are green rather than the yellow in many buttercups and they stand as a dome in the centre of the flower. The leaves are very serrated (see the Latin name sceleratus) on a tall, fleshy stem that can reach two feet tall. This not like the buttercup on your lawn! This is not a plant of grassy areas and verges, this is species found on muddy areas in marshes, usually fresh water but not always.
This is a very toxic plant, it is known as the cursed buttercup in India, and can cause blisters if handled and it certainly should not be eaten! That said it has medicinal uses and extracts of it are used to treat infected wounds.