Water dropwort

The water dropworts, Oenanthe /ɔɪˈnænθiː/, are a genus of plants in the family Apiaceae. Most of the species grow in damp ground, in marshes or in water.

Several of the species are extremely poisonous, the active poison being oenanthotoxin. The most notable of these is O. crocata, which lives in damp, marshy ground, and resembles celery with roots like a bunch of large white carrots. The leaves may be eaten safely by livestock, but the stems, and especially the carbohydrate-rich roots are much more poisonous. Animals familiar with eating the leaves may eat the roots when these are exposed during ditch clearance – one root is sufficient to kill a cow, and human fatalities are also known. It has been referred to as the most poisonous of all British plants, and is considered particularly dangerous because of its similarity to several edible plants.