This monotypic circumboreal genus has a widespread northern and western range in North America, and may only be adventive in some southeastern states (W). It is a diploid (2n = 12) that is reportedly an annual, biennial or short-lived perennial (Cr, FNA 7, W). In Ky. it is known only from OLDH (DHL) and SHEL (KY-Agr.). There is also a general report from c. Ky. by Linney (1882), under the synonym Arabis perfoliata Lam.