Summer Flower Gallery. Gazania (Treasure flower). A native of South Africa, the Gazania rigens is also known by its common name, the Treasure flower, in reference to its rich flowers. It is reportedly named in honor of Theodore de Gaza, a 15th-Century Greek scholar. A perennial in its native climate and in USDA zones (8b-24), it is frost hardy to 15 F. In colder climates, gardeners grow them as annuals.