Garden and Flowers

Osteospermum is a real maverick among the compositae family. Usually, a border of sterile ray flowers - those of a marguerite, for example - attracts insects to the center of the flower with its tubular florets; these are fertile and develop the seed. In osteospermums, however, the tubular florets are sterile and the seed is formed in the fertile ray flowers. You can see this phenomenon yourself after the plants have flowered. The brownish-black seeds, which are very large and hard, develop into wreaths round the centers of the faded flowers. This characteristic distinguishes Osteospermum from Dimorphotheca, a genus dealt with elsewhere in this encyclopedia, with flowers that in other respects closely resemble those of Osteospermum.

For several years now, these magnificent plants have been on sale on a quite a large scale from March onwards. Plants that have been properly hardened off will tolerate a few degrees of frost. The wild species and older cultivars do not flower until after a cold period. More modern cultivars do not need that cold induction. They also stay far more compact than the bushy plants from South Africa.

Chemical growth inhibitors are still used to keep the plants compact, but they are no longer required for all cultivars. They are on sale as flowering plants with a height and spread of about 8 in. When in flower, plants in a sunny position grow to about 20 in tall, sometimes to about 39 in in the shade. Their main flowering season is in spring, but they continue to bear flowers well into autumn. It is therefore important to ensure that they have a very sunny position in loose, well-drained soil. If you are growing them in pots, avoid letting the soil dry out completely and provide some extra food to extend the flowering season.

Osteospermum ecklonis is the main ancestor of the current hybrids, but other species such as Osteospermum jucundum were bred in as well. Although some cultivars may be propagated by seed - sown under glass in March-April - those mentioned below are typical plants grown from cuttings. In that way, their essential characteristics are best retained, and improvers can secure their plant breeder’s rights to their products. Only licence-holders are entitled to cultivate the plants on a commercial scale. In my opinion, the plants will, under glass, tolerate temperature of about 14 °F.

Osteospermum ‘Bamba’: broad ray flowers, almost white as they emerge from the buds, but soon changing to violet.

Osteospermum ‘Buttermilk’ : pale yellow flowers developing from brown-striped buds.

Osteospermum ‘Congo’ : relatively small, pale violet-pink flowers with blue eyes. Osteospermum ‘Lusaka’ : ray flowers more oblong than those of ‘Bamba’, and slightly lighter in color.

Osteospermum ‘Pemba’: the ray flowers are pressed together to form tubes halfway along. Osteospermum ‘Volta’ : lilac pink, subsequently paling to almost white. Osteospermum ‘Zulu’: soft yellow.