I am not really certain. Possibly several or more, but it could be just one, that has been kept from flowering. Usually, the ordinary one's can make it through most winters here, eventually flowering & then that puts an end to it. It can be treated as annual, be biennial, or act a short lived perennial. I also like Salvia argentea, for the much larger fuzzy grey leaves, all except for the flowers! They have started to come out with some newer varieties of "Dusty Miller", with various leaf forms, fairly recently.
