Whether African Daisies (Osteospermum spp.) are classified as annuals or perennials is a nuanced question in botany, as the answer depends heavily on the specific environmental conditions, primarily temperature. From a strict plant life cycle perspective, Osteospermum are herbaceous perennials. However, their sensitivity to cold temperatures means they are very often grown and function as annuals outside of their preferred climate range.
Genetically, Osteospermum species are classified as tender herbaceous perennials. In their native habitats of South Africa, they grow year after year, surviving through their dormant periods to resume growth and flowering when conditions become favorable again. They possess a semi-woody crown at the base of the plant from which new stems and foliage emerge each growing season. This regrowth from persistent rootstock and crown structures is a definitive characteristic of perennial plants, not annuals which complete their entire life cycle from seed to death within a single season.
The primary factor that dictates the lifecycle expression of African Daisies is temperature, specifically their intolerance to freezing conditions. They are best suited to USDA Plant Hardiness Zones 9 through 11. In these zones, which experience minimal or no frost, Osteospermum will reliably behave as perennials, remaining evergreen or dying back slightly before putting on vigorous new growth in the spring. Their root systems survive the winter, and the plant's energy is stored for the next season's growth, a key trait of perennial species.
In regions where winter temperatures consistently drop below freezing (approximately 25°F or -4°C), the plant's cellular structure cannot survive. The freeze damage kills the above-ground foliage and, critically, the root system. Once the root crown and roots are destroyed by frost, the plant cannot regenerate, leading to its death. For gardeners in these colder zones (typically Zones 8 and below), the plant is incapable of surviving the winter outdoors. It is therefore planted in the spring, flowers profusely throughout the warm season, and is killed by the first hard frost in autumn, completing its presence in the garden in one single season. This is the functional definition of an annual in horticultural practice.
Gardeners in colder climates can employ strategies to overcome the plant's cold sensitivity and preserve its perennial nature. The most common method is to grow Osteospermum in containers. Before the first frost, the containers can be moved to a protected environment such as a cool greenhouse, garage, or bright indoor windowsill where temperatures remain above freezing. During this dormancy period, watering is significantly reduced. The plant is then moved back outside after the danger of frost has passed in spring. Alternatively, in mild winter regions, applying a thick layer of mulch around the plant's base can sometimes provide enough insulation to protect the crown and roots from brief, light frosts.
