Osteospermum is a genus of flowering plants in the tribe Calenduleae, one of the smaller tribes within the sunflower and daisy family Asteraceae, order Asterales. It was named by Carl Linnaeus in 1753 and comprises approximately 74–136 accepted species, the majority of them native to southern and eastern Africa and the Arabian Peninsula.
Plants in this genus are commonly known as daisybushes or African daisies, with individual species also called Cape daisy, South African daisy, and blue-eyed daisy. They bear alternate, lanceolate leaves — occasionally opposite — that are typically green, though variegated forms exist; hardy types often have toothed leaf margins. The characteristic flower heads are daisy-like composites made up of disc florets and ray florets. Disc florets are pseudo-bisexual and appear in shades of blue, yellow, and purple, often with a distinctive dark blue center before pollen is shed. Ray florets are female and range across white, cream, pink, purple, mauve, and yellow. Certain cultivars, such as ‘Pink Whirls’, produce distinctively spooned or spoon-shaped petals. Many species produce a second flush of flowers in late summer, triggered by cooler night temperatures.
Osteospermum is a sister taxon to the closely related genus Dimorphotheca. Plants of the World Online and the South African National Biodiversity Institute recognize a broad circumscription of the genus that subsumes Chrysanthemoides, Oligocarpus, and related segregates; other authorities treat these as separate genera. Several horticulturally important species once listed under Osteospermum — including the popular Osteospermum ecklonis and Osteospermum fruticosum — have been reclassified as Dimorphotheca, though they continue to be sold and grown under the Osteospermum name in nurseries and gardens worldwide.
Osteospermum species are widely grown as ornamentals, valued for their long flowering season, tolerance of poor soil, salt, and drought, and their broad palette of cultivar colors. They are a staple of summer bedding displays in parks and gardens across temperate regions.
Etymology
The name Osteospermum was coined by Carl Linnaeus in 1753, derived from the Ancient Greek words ὀστέον (ostéon), meaning “bone”, and σπέρμα (spérma), meaning “seed” — a reference to the hard, bony texture of the seeds.
Distribution
Osteospermum has approximately 70 species native to southern and eastern Africa and the Arabian Peninsula, with the greatest diversity concentrated in the Cape Floristic Region and broader southern Africa.
Taxonomy Notes
Osteospermum is placed in tribe Calenduleae within Asteraceae and is the sister taxon to Dimorphotheca. Plants of the World Online and the South African National Biodiversity Institute accept a broad genus circumscription that includes the segregate genera Chrysanthemoides and Oligocarpus; other authorities recognize these as distinct. Several horticultural taxa long known as Osteospermum — including O. ecklonis and O. fruticosum — are treated as Dimorphotheca under the strict circumscription.
Cultivation
Osteospermum thrives in warm, sunny positions with rich soil, though it tolerates poor soil, salt, and drought well. Modern cultivars flower continuously when kept watered and fertilized, and dead-heading is generally unnecessary as they do not set seed readily. Container-grown plants are sensitive to complete soil drying — when this occurs plants enter a dormant “sleep mode,” aborting flower buds and recovering poorly — while overwatering after a dry spell can cause root rot.
