Seeds from Tree Gardenia Gardenia thunbergii, Starry Gardenia or white gardenia. Native to South Africa this small tree is densely twiggy and rigid with smooth light-grey bark. The leaves are smooth, shiny, whorled, and clustered at the ends of branches. The many flowers are large, white, extremely fragrant and about 3 to 4 inches in diameter. Hardy in zones 8-11 and prefers full sun to part shade.