Osteospermum, a genus of plants in the Calenduleae, is a small group from the Asteraceae family. Commonly known as African daisy, they consist of about 70 species indigenous to south and east Africa including the Arabian Peninsula, most plants today are hybrids and cultivars derived from O. jucundum, O. ecklonis, and other species.
These plants range from 1–3 feet high and 1–2 feet wide. The green leaves alternate but some variegated varieties exist and vary by shape – lance-like or ovate and smooth, lobed, or toothed in hardy types. These perennial plants have a quick rate of growth, flowering about two months after germinating from seeds. Very hardy in USDA zones of 10 – 11, they are planted as annuals in other zones.
The flowers are similar to regular daisies as their petals radiate from a central disk and even belong in the same Asteraceae family, but their coloring is dissimilar to the classic daisy. When introduced to the world, some people initially thought that the flowers were dyed. The central disks of the flowers can even look like they’re painted. Petals are smooth and flat or radiate outwards in the shape of a tubular spoon. The flowers commonly open in the day, close at night, and in overcast weather. However, some new cultivars, including ‘4D Berry’, ‘4D Pink’ and ‘4D Silver’ don’t close at night.
The flower consists of ray florets and disc florets, coming in several colors like yellow, blue, and purple. Hardy types, until yellow pollen appears, typically have a dark blue center. The female ray florets have diverse colors of pink, purple, mauve, white, cream, and yellow.
Several species bloom a second time in late summer when they are stimulated by cooler temperatures at night. Hardy types profusely flower in spring but don’t produce a second set of flowers.
They are often grown as summer bedding arrangements in gardens and parks. They grow well either in containers or in the ground. They stop flowering in hot spells at the height of summer.
They produce more flowers under full sun and less in partial shade, although plant growth won’t be affected.
While they are a little drought-tolerant when mature, water them at least once weekly. During periods of extreme heat or drought, growth and flowering slow down as they go dormant. Keep the soil moistened but don’t overwater, as soggy soil encourages diseases such as root rot. They need more water if grown in containers and soil shouldn’t be allowed to dry out. If this happens, the plants will go dormant, flower buds will die and they won’t easily begin flowering again.
Humidity usually isn’t a problem for these plants, provided that they have enough air circulation and appropriate watering, and excellent soil drainage.
They produce more flowers in mild weather and can handle night temperatures down to about 40°F, although frost will damage or kill the plants. Their preferred growing temperature ranges from 65 – 80°F. Protect them from lower temperatures when they are cultivated in containers.
They prefer rich organic soil with good drainage and somewhat acidic pH, add compost or organic matter when planting to add nutrients and improve drainage.
If you grow these plants in containers, the root ball might get congested in time, affecting growth so repot them into larger containers with good drainage.
The seeds are viable for just 2 – 3 years, so check the date on the seed package. The majority of modern varieties are hybrids that rarely produce seeds and don’t grow true from harvested seeds from your existing plants, but these plants can be easily propagated from cuttings.
Propagation from Seeds
The hybrids sold at garden centers are typically available as seeds, but you might be able to find seeds of some pure species/varieties, such as O. ecklonis.
Around 2 months or so before spring begins, sow seeds directly in a pot of regular potting mix. Lightly press down the seeds since light is necessary for germination. Place the pot under bright indirect light and keep the mix moist until the seeds germinate. Continue watering the seedlings until the weather becomes warmer. Plants started indoors must be hardened off two weeks before planting them outdoors. Pinch back seedlings after planting to encourage thicker growth.
First, fill a pot with a seed-starting mix and lightly moisten the mix. Then take 2 – 3 inch long cuttings with two leaf nodes. Remove any flower buds and lower leaves and plant the cutting in the mix.
Cover with a transparent plastic packet and place the pot under bright indirect light with temperatures between 60 and 68°F. The cutting should be rooted in 4 – 6 weeks. Transplant to a container filled with rich organic soil or outdoors in your garden.
These flowers need plenty of food to bloom and grow at their best. Other than adding compost to the soil, a balanced fertilizer suitable for flowering plants should be applied every month throughout their growing season. Potted plants might require more frequent feeding.
After flowers wither and die, remove them and any dead leaves to produce more flowers and stimulate growth.
Pruning will also stimulate bushy growth, continual production of flowers, reduce overcrowding, promote good ventilation, and allow the plants to receive more sunlight. This also helps prevent powdery mildew and gray mold and pests like aphids and whitefly.
If these plants are kept in stress-free conditions and under proper care, there are not many diseases or pests that can trouble them. However, in humid or damp conditions watch out for powdery mildew or gray mold fungal diseases. These diseases will damage or discolor foliage. Pruning will improve air circulation and prevent these diseases. Use a suitable fungicide if needed.
Common plant pests like whitefly and aphids can be a problem, particularly for stressed plants. They can be controlled with insecticidal soap and/or neem oil.
They generally don’t need plenty of encouragement to flower, but several conditions can affect blooming such as poor nutrition. If the plants don’t bloom well, increase feeding to every 2 to 3 weeks. As mentioned earlier, potted plants require more fertilizer, extreme heat and under-watering can also play a role in shading the plants and increasing watering frequency, particularly in hot weather. Insufficient light will cause leggy growth and fewer flowers. Transplant them to a sunnier location.
Animals such as groundhogs and deer love to feed on these plants. The only protection against these animals is strong fencing.