North American plant genus in the family Asteraceae. All of its members are selenium indicators and usually contain sufficient selenium, in the form of selenocompounds, to cause poisoning manifested by alopecia, lameness, laminitis, hoof deformity.
The recorded species are X. glabriuscula, X. parryi, X. tortifolia, X. venusta, X. villosa. All called also woody aster. Formerly classified in genus Aster.