Dimorphotheca is a small genus of flowering plants in the Astereaceae family. They are native to southern Africa, but are widely grown as ornamentals for their bright orange, yellow, or white flowers. The plants are well-adapted to growth in hot, dry climates and can provide spring color to xeriscape plantings in desert areas. Commonly known as the African daisy or cape marigold, these types of plants have become naturalized in the western U.S. and can be invasive in warm climates.
There are several species of dimorphotheca that are grown horticulturally. The most common is Dimorphotheca sinuate, more commonly known as glandular cape marigold. An alternate scientific name for this plant is Dimorphotheca aurantiaca. Other plants share the common name of African daisy, including flowering plants in the genus Osteospermum.
These hairy plants are annuals and do not live longer than one year. They grow to be 1 to 1.5 ft (0.3-0.45 m) tall, and are generally branched. Each plant produces multiple flowers, each growing on a single stalk. The flowers are 2.4 to 5.6 (6-14 cm) wide. In addition to being used for color in sunny flower beds, African daisies are also used as cut flowers.
Dimorphotheca plants have an outer and inner ring of flowers. They produce two different types of seeds with different germination requirements, depending on which type of flower the seeds are produced from. This variability helps the plants to survive in extreme climates. The seeds have also been examined as a potential crop source for seed oil.
In desert areas, such as southern Arizona or southern Africa, dimorphotheca seeds germinate when watered by fall and winter rains. The plants bloom profusely in the spring. If the season is not very wet, the plants will need to be watered every week. They grow when conditions are favorable, then survive drought and heat as a seed. Seed heads should be left on the plants, so they will produce the plants for the next year.
Often, in cooler climates, seeds of these African daisies are germinated indoors before seedlings are planted out in the garden. The seeds should be planted inside at 68°F (20°C), or in a cold frame four weeks before the estimated date of the last frost. The plants are not cold hardy and will be killed by a frost. Seeds might survive the winter if they are fall on bare ground.
In these more temperate regions, dimorphotheca is recommended as an annual for hot and dry conditions. The plants will need to be watered as they develop. Once the plants have become established, they are more likely to survive some neglect than other annuals.