Dimorphotheca fruticosa – African Daisy
Dimorphotheca fruticosa (L.) Less. is an evergreen, trailing perennial in the daisy family (Asteraceae), native to the coast of South Africa. For decades, gardeners knew it as Osteospermum fruticosum (L.) Norl., and it still appears under this name in most nursery catalogs, especially in California and the Mediterranean basin. Modern taxonomic treatments, including Plants of the World Online and the South African SANBI, have nevertheless moved it back into the genus Dimorphotheca, to which Lessing assigned it as early as the 19th century. Linnaeus described the species in 1760 as Calendula fruticosa, and its synonyms also include Blaxium decumbens, Calendula diffusa, and Osteospermum riparium.
In English-speaking countries, the plant is known as trailing African daisy and is one of the most commonly planted ground covers in Mediterranean climates. Its white flower heads with purple centers, fleshy leaves, and remarkable tolerance of salty winds have made it almost commonplace from California to Australia, and it has even become naturalized in New Zealand. In cooler regions of Europe, it remains a seasonal or container plant, valued for its rapid growth and long, abundant flowering from late spring to autumn.
Botanical description and plant habit
This is a low perennial with trailing or slightly ascending stems that are shortly hairy and become woody at the base with age, which explains the specific epithet fruticosa, meaning shrubby. The plant usually reaches 10–50 cm in height, while a single specimen spreads 60–100 cm wide; stems that come into contact with moist soil root and form dense mats. The leaves are alternate, stalked, obovate to spatulate, fleshy, and semi-succulent, with finely toothed margins, up to 10 cm long and 2.5 cm wide. Their thick blades store water and protect the plant from the drying effects of wind and salt.
The flower heads grow singly on bare stalks held above the foliage. The ray florets are white on the upper side and lilac to purple underneath, so the buds and flower heads closed at night have a completely different, pastel color from those that are open. The tubular florets in the center of the flower head range from reddish violet to dark purple, often with a metallic, bluish sheen. The fruit is an achene about 6 mm long, smooth and triangular in cross-section, dispersed by the wind. The generic name Dimorphotheca, derived from Greek and literally meaning “two-shaped fruit,” refers to the fact that in plants of this genus, the achenes from the ray and tubular florets have different structures.
Growth rate and development
Dimorphotheca fruticosa is an exceptionally fast-growing plant. A young plant planted in spring in a sunny location can cover an area one metre in diameter within a single season, while in mild climates it covers slopes and walls within one or two years. The Royal Horticultural Society (RHS) states that it reaches its full size in 2–5 years; however, when grown as an annual, it is fully decorative already in its first year. With age, the centre of the clump becomes woody and sparse, so in regions where the plant overwinters, the shoots are shortened by about one-third every year at the end of winter, and older specimens are replaced with rooted cuttings.
Flowering and propagation
In its native range, the species flowers from June to October, which in the Southern Hemisphere corresponds to the period from winter to early summer; in New Zealand, flowering has been observed from August to January. In Europe, flowering begins in late spring and continues until autumn, although during the hottest periods plants often take a break before flowering again when the nights become cooler. The flower heads, like those of other African daisies, open in the morning sunlight and close in the evening and on cloudy days, which is a natural characteristic rather than a sign of cultivation problems. The flowers are visited by various insects, including bees and butterflies.
In addition to seeds, the species is very easy to propagate vegetatively. SANBI recommends stem cuttings taken in spring or autumn and rooted in a mixture of perlite and bark, while the RHS recommends softwood cuttings in late spring and semi-ripe cuttings at the end of summer, taken from non-flowering shoots. This is how favourite specimens are kept through the winter in cooler regions: several rooted shoots take up considerably less space on a windowsill than the entire parent plant. Shoots that come into contact with the ground also root spontaneously, so layering is another simple method.
Distribution and natural habitat
The species' natural range extends along the coast of South Africa from Saldanha Bay in the Western Cape, through the Eastern Cape, to KwaZulu-Natal. The plant inhabits sandy beaches, coastal dunes and rocky cliffs, usually in the first line of vegetation exposed to sea breezes, salt spray and gale-force winds. The western part of its range has a Mediterranean climate with wet winters and dry summers, while the eastern part has summer rainfall and warm, humid winters; this range of conditions explains why the species adapts so well to gardens around the world.
As an ornamental plant, Dimorphotheca fruticosa has been introduced to California, the Mediterranean coast, Australia and New Zealand. In New Zealand, it became naturalized in 1977 and is now widespread along the coasts of the North Island, where it is classified as an environmental weed that displaces native dune vegetation. This is a warning to gardeners in regions with mild winters not to plant it near natural coastal habitats. In temperate European climates, this risk does not exist because the plant does not survive the winter outdoors. In the Red List of South African Plants, the species is classified as Least Concern.
Environmental requirements and tolerance
Full sun is the most important requirement; in partial shade, the stems become leggy and flowering is reduced. The soil should be light, sandy or gravelly, poor to moderately fertile and very well drained. The RHS lists chalky, sandy and light loamy soils as suitable, noting that the plant tolerates poor soil, salinity and drought. Its water requirements are moderate: during the growing season in its native range, it is watered up to three times a week, although established plants withstand long periods without rain. Constantly wet soil is the most common cause of failure, as it leads to root and stem-base rot.
In terms of temperature, the species is on the borderline of frost-hardy plants: the RHS gives it an H3 rating, meaning tolerance of short-term temperature drops to around -5 °C, while American sources list USDA zones 9–11 and survival at around -6 °C. Plants die during prolonged frost or when frost coincides with wet soil. It tolerates high temperatures well, but stops flowering during extreme heat with dry air. The RHS lists aphids, downy mildew and verticillium wilt among its pests and diseases, although in practice the plant rarely becomes diseased when provided with good drainage and an airy position. It is worth remembering that the stems may be harmful to rabbits and rodents if eaten, although the plant is not considered poisonous to humans, dogs or cats.
Cultivation in temperate climates
In cooler regions of Europe, the African Daisy is grown in two ways. The first is to treat it as an annual: after the last frosts, it is planted in a sunny bed, on a slope or in a gravel garden, where it forms a flowering carpet until autumn and completes its life cycle as winter approaches. The second method is to grow it in pots, window boxes and hanging baskets filled with a free-draining growing medium, such as universal potting soil mixed with one-third sand or perlite. In autumn, before the first severe frosts, such plants are moved to a bright, cool room at a temperature of 5–10 °C, and watering is reduced to a minimum so that the root ball does not dry out completely.
In early spring, overwintered plants are pruned by about one third, repotted in fresh growing medium and gradually hardened off before being returned outdoors. During the season, a balanced fertilizer every 4–6 weeks or a single application of slow-release fertilizer in spring is sufficient; excess nitrogen produces lush foliage at the expense of flowers. Regularly removing spent flower heads significantly extends flowering. The plant tolerates pruning very well, so overly long shoots can be shortened at any time during the season.
Uses in ornamental gardening
In Mediterranean and Californian climates, Dimorphotheca fruticosa is one of the main ground-cover plants: it is planted on roadside embankments, retaining walls and slopes, where it stabilizes the soil and limits erosion, and in coastal gardens it is one of the few species that can withstand the first line of salty wind. Popular cultivars and hybrids, such as 'Whirligig' with spoon-shaped rolled ray florets and pink-flowering forms, are derived from this species and the closely related Osteospermum jucundum. In Central and Northern Europe, the plant is used in containers, balcony boxes, hanging baskets and seasonal beds, where its white flower heads, which open in the sun, combine well with lavender, gazania, sedums, spurges and low ornamental grasses.
Who this species is for
This plant is for people who want to quickly and inexpensively cover a sunny, dry spot with a flowering carpet, as well as for owners of south-facing balconies and terraces where many other plants wither. It will appeal to anyone who likes low-maintenance plants: all it needs is sun, well-drained soil and moderate watering. However, it requires accepting that in a temperate climate it is a seasonal guest or a resident of a cool conservatory and bright stairwell during winter. People with gardens on coasts with mild winters should remember its tendency to naturalize.
Summary
Dimorphotheca fruticosa, known as Osteospermum fruticosum and African Daisy, is a fast-growing, evergreen ground-cover perennial from the dunes of South Africa, with fleshy leaves and large white flower heads with purple centers, flowering from late spring to autumn. It tolerates drought, salty wind and poor soil, but not winter outdoors in the ground in a temperate climate, so in cooler parts of Europe it is grown seasonally or in containers overwintered in a cool, bright room. The species is not threatened and has Least Concern status in its native range (IUCN/SANBI: Least Concern).
