Osteospermum
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 White-flowering Osteospermum with violet-edged petals. | ||||||||||||||||
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Osteospermum is genus belonging to the Calenduleae, one of the smaller tribes of the sunflower family (Asteraceae). It used to belong to the genus Dimorphoteca, but only the annual species remain in this 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.
The scientific name is derived from the Greek osteon (= bone) and Latin spermum (= seed). It has been given several common names : African Daisy, South African Daisy, Cape Daisy and Blue-eyed Daisy.
There are about 50 species, native to Africa, 35 species in southern Africa, and southwestern Arabia. They are half-hardy perennials or subshrubs. Therefore they don't survive outdoor wintery conditions, but there is still a wide range of hardiness.
Their alternate (rarely opposite) leaves are green, but some beautiful variegated forms exist. The leaf form is lanceolate. The leaf margin is entire, but hardy types are toothed.
The flowers consists of disc florets and ray florets, growing solitary 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 show a dark blue center in the disc.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. Hardy types show profuse flowering in the spring, but they don't get a second flush of flowers.
Species
- Osteospermum acanthospermum
- Osteospermum amplectens
- Osteospermum attenuatum
- Osteospermum australe
- Osteospermum barberae
- Osteospermum burttianum
- Osteospermum calendulaceum L. f. : Stinking Roger (synonym of Oligocarpus calendulaceus)
- Osteospermum caulescens
- Osteospermum clandestinum (synonym of Tripteris clandestina)
- Osteospermum dentatum
- Osteospermum ecklonis (DC.) Norl. : Cape Marguerite, Blue-and-white Daisybush
- Osteospermum fruticosum (L.) Norl. : Trailing African Daisy, Shrubby Daisybush
- Osteospermum grandidentatum : Yellow Trailing Daisy
- Osteospermum grandiflorum
- Osteospermum hyoseroides
- Osteospermum imbricatum
- Osteospermum jucundum (Phill.) T. Norl.
- Osteospermum microphyllum
- Osteospermum monocephalum (Oliv. & Hiern) Norl.
- Osteospermum muricatum
- Osteospermum oppositifolium (synonym of Tripteris oppositifolia)
- Osteospermum pinnatum
- Osteospermum polygaloides
- Osteospermum potbergense AR Wood & B. Nord
- Osteospermum rigidum
- Osteospermum rotundifolium
- Osteospermum sinuatum (DC.) Norl. (synonym of Tripteris sinuata)
- Osteospermum spinescens
- Osteospermum subulatum DC.
- Osteospermum tomentosum
- Osteospermum triquetrum L. f.
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 to Oligocarpus.
New species are still being discovered, such as O. australe, O. burttianum and O. potbergense.
Osteospermum flowers are popular in the nursery trade. Propagation is mainly carried out by cuttings. Many hybrids and cultivars have been grown with a large array of tropical colors.
One of the most popular cultivars is Osteospermum 'Pink Whirls', creating a stunning show in any garden. Its 13-18 spooned petals give the impression of an optical illusion. The green, somewhat glossy leaves are opposite.
Reference work
Nordenstam, B. 1994. Tribe Calenduleae. In: Asteraceae, cladistics and classification (ed. K. Bremer). Timber Press, Oregon, pp. 365-376.
External links
A phylogenetic study of the Calenduleae - Bertil Nordenstam & Ida Trift (http://www.biologie.uni-hamburg.de/b-online/ibc99/ibc/abstracts/listen/abstracts/3885.html)
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