Most cultivated roses have double blossoms. This means that the flower has many petals arranged in several layers. Some cultivated roses lack thorns. Roses grow in many parts of the world, in various soils and climates. They do especially well in temperate and mild climates.
Roses thrive under cultivation, and thousands of varieties have been developed.
Others disappear because plant breeders produce better ones. For example, the American beauty rose was once popular but is no longer grown commercially. It is a hybrid perpetual, famous for its fragrant crimson flowers. The rose is the national flower of the United States and Iran. Several states and a Canadian province have also chosen the rose as their official flower.