''Oxypolis rigidior'', known as cowbane, common water dropwort, stiff cowbane, or pig-potato, is a species of flowering plant in the carrot family native to eastern North America. It is a perennial wildflower found in wet habitats. ''Oxypolis rigidior'' is poisonous to mammals.

Description

''Oxypolis rigidior'' is 2–6 foot tall perennial herb of eastern North America. Its leaves are compound, odd-pinnate with 7-11 leaflets, and have variable shape. Umbels of 3 mm white flowers appear August to October. Flat fruits with conspicuous "wings" appear October through November. The variable leaf shape may make identification challenging.

Water hemlock ''Cicuta'', commonly known as water hemlock, is a genus of four species of highly poisonous plants in the family Apiaceae. They are perennial herbaceous plants which grow up to tall, having distinctive small green or white flowers arranged in ...

, a related very poisonous species, which sometimes even shares the common name "cowbane", is similar, as is the closely related Savanna cowbane (''

Oxypolis ternata ''Oxypolis'' is a small genus of North American flowering plants in the carrot family known as cowbane, water dropwort, dropwort, hog-fennel, and pig-potato. , Kew's Plants of the World Online accepts four species in the genus ''Oxypolis'': *' ...

'').

Taxonomy

Two varieties have been described, ''O. rigidior'' var. ''rigidior'' and ''O. rigidior'' var. ''ambigua''.

Toxicity

Both roots and top parts are poisonous to mammals.

References

{{Taxonbar, from=Q17134564 Apioideae Flora of North America