About Oxypolis rigidior (L.) Raf.
Oxypolis rigidior is a perennial herb that grows 2 to 6 feet tall, native to eastern North America. Its leaves are compound and odd-pinnate, with 7 to 11 leaflets, and have variable shape. Umbels of 3 mm white flowers bloom from August to October. Flat fruits with noticeable "wings" develop from October through November. Variable leaf shape can make this species difficult to identify. It resembles water hemlock, a related, extremely poisonous species that sometimes shares the common name "cowbane"; it is also similar to the closely related Savanna cowbane (Oxypolis ternata).
Sources disagree on the toxicity and edibility of Oxypolis rigidior. Both the aboveground parts and roots have been reported to be poisonous to mammals, including cattle. However, some sources consider the plant edible and safe. Author Sam Thayer states that claims of this plant being poisonous to livestock are widespread and incorrect. He reports that the plant's tubers are edible, and describes them as "fantastic in any way you'd use a potato". Thayer notes that the plant's shoots and leafy greens are not poisonous, though he does not state whether these parts are edible. He refers to the plant as "Cherokee swamp potato", referencing its use in Cherokee cuisine. Thayer also warns that Oxypolis rigidior should only be collected with great caution, due to its close resemblance to poisonous water hemlock.
