Osteospermum, is a genus of flowering plants belonging to the Calenduleae, one of the smaller tribes of the sunflower/daisy family Asteraceae. They are known as the daisybushes or African daisies. Osteospermum used to belong to the genusDimorphotheca, but only the annual species remain in that genus; the perennials belong to Osteospermum. The genus Osteospermum is also closely related to the small genus Chrysanthemoides, such as C. incana and C. monilifera.
Their alternate leaves are green, but some variegated forms exist. The leaf form is lanceolate. The leaf margin is entire, but hardy types are toothed. The daisy-like composite flower consists of disc florets and ray florets, growing singly at the end of branches or sometimes in inflorescences of terminal corymbose cymes. The disc florets are pseudo-bisexual and come in several colors such as blue, yellow and purple. The hardy types usually show a dark blue center in the disc until the yellow pollen is shed. The ray florets are female and are found diverse colors such as white, cream, pink, purple, mauve to yellow. Some cultivars have "spooned" petals such as "Pink Whirls". Many species flower a second time late summer, stimulated by the cooler night temperatures. Hardy types show profuse flowering in the spring, but they do not get a second flush of flowers.
A phylogenetic study has revealed that several changes had to be made to this genus:
Osteospermum section Blaxium belongs in the genus Dimorphotheca
the subgenus Tripteris had to be separated from Osteospermum
the genus Oligocarpus has to be separated from Osteospermum
Osteospermum sanctae-helenae, endemic to St. Helena, belongs toOligocarpus.
New species are still being discovered, such as O. australe, O. burttianum and O. potbergense.
Distribution
There are about 70 species native to southern and eastern Africa and the Arabian peninsula.
Cultivation
Osteospermum are popular in cultivation, where they are frequently used in summer bedding schemes in parks and gardens. Numerous hybrids and cultivars have been grown with a wide range of tropical colors. Yellow cultivars tend to have a yellow center. Plants prefer a warm and sunny position and rich soil, although they tolerate poor soil, salt or drought well. Modern cultivars flower continuously when watered and fertilised well, and dead-heading is not necessary, because they do not set seed easily. If planted in a container, soil should be prevented from drying out completely. If they do, the plants will go into "sleep mode" and survive the period of drought, but they will abort their flower buds and not easily come back into flower. Moreover, roots are relatively susceptible to rotting if watered too profusely after the dry period.
Cultivars
Most widely sold cultivars are grown as annuals, are mainly hybrids of O. jucundum, O. ecklonis and O. grandiflorum and can be hardy to -2 °C. If hardy, they can be grown as perennials or as shrubs. Cultivars :
