Blepharizonia is a genus of flowering plants in the aster family, Asteraceae. There are two species, both endemic to California. They are known generally as big tarweeds. The genus long included only the single species B. plumosa, which was divided into two subspecies. Studies of the plant indicated that the subspecies had low interfertility, rarely interbreeding when growing together. They were also evolutionarily divergent and had significant morphological and ecological distinctions. One of the subspecies was elevated to species status and is now usually treated as B. laxa.