Berkheya radula, or Sun Daisy, is a prickly perennial herb native to South Africa. Leaves are mainly in basal rosettes with leaves being linear-elliptic. They are rough on the upper side and white felted on the underneath side. Margins are coarsely serrulate-dentate with marginal spines. The leaves of plants grown in containers were 12 inches (30 cm) long by 3.5 inches (9 cm) wide and medium green. Plants in nature will reach up to 3 ft (1 m) tall and wide. These are interesting plants to grow and watch their development. Although the plants are hardy in USDA zone 8-11, I believe they could become very weedy if planted in the landscape.
Blooming: The plants we grew bloomed this spring from seed planted 1 year ago. The capitulum has irregular spiny wings and glandular hairs. As the flower buds started forming, they have a nodding appearance and finally grow straight up at the blooming time. The yellow daisy ray flowers are what I call creamy yellow with darker disk flowers.
Culture: Berkheya radula needs full sun to light shade with a well-grained soil mix. We used a soil mix consisting of 2 parts peat to 2 parts and 1 part loam. The plants are well watered and allowed to dry somewhat before watering again. We fertilized the plants only once during the growing season with a balanced fertilizer diluted to 1/2 the strength recommended on the label. In nature, I believe plant would be more drought tolerant than plants grown in containers. In late September, the plants are moved to the cool rooms for over wintering. The plants are deciduous and die back to the container during this time. Water is applied occasionally, but the soil is not allowed to stay wet.
Propagation: Berkheya radula is propagated by seed. Seed should be sown in the spring and will germinate in 30-60 days from sowing.
Berkheya radula was featured as Plant of the Week March 27-April 2, 2009.
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Cal's Plant of the Week was provided as a service by the University of Oklahoma Department of Microbiology & Plant Biology and specifically the late Cal Lemke, who used to be OU's botany greenhouse grower and an avid gardener at home as well. If the above links don't work, then try the overview site. You may also like to look at the thumbnail index. ©1998-2012 All rights reserved.