Useful Techniques in the Successful Production of Osteospermum

Osteospermum is a colorful new potted crop that could potentially serve to fill in the retail gap between Easter and when consumers are able to get into their gardens. Osteospermum ecklonis or the Cape daisy is a member of the Aster family and is native to the Cape region of South Africa. Osteospermum is an erect plant with dark green lobed leaves. The flowers are daisy-like that, depending on cultivar can vary from white to purple with the bright yellow pollen in the center disc florets providing an appealing contrast (Photo 1) (Photo 2) (Photo 3) (Photo 4) (Photo 5).

The keys to the successful commercial production of Osteospermum are controlling height and the timing of flowering. In its native habitat, Osteospermum is a perennial woody shrub that grows 3 to 5 feet high. Moreover, flowering is unpredictable and individual flowers do not bloom synchronously in a single flush. We therefore initiated research designed to determine what cultural practices are necessary to produce are well-shaped plant full of flowers in a six inch pot.

We first turned our attention to flowering. At first we attempted to manipulate flowering by altering the photoperiod. Since Osteospermum flowers in its native habitat in mid- summer, we reasoned that the long days of summer would promote flowering. However we found that even ultra-long photoperiods of 18 hours had little effect on flowering. However, since this species is a perennial, another possibility is that cool temperatures may trigger more profuse flower production; that is perhaps vernalization is required as in many other (but not all) perennial species. In order to test this, we received rooted cuttings of two Osteospermum cultivars, 'Nairobi' and 'Lady', from the Paul Ecke Ranch in October 1996. The cuttings were transplanted into 6" pots and allowed to grow and establish root systems in a warm (75EF day, 65EF night) greenhouse. After four weeks, plants were pinched, leaving 7 to 8 leaves, and then moved to a cool greenhouse maintained between 45 and 55EF. After 2, 4, or 6 weeks groups of each cultivar were then returned to the warm greenhouse. A group was maintained in the warm greenhouse as a check, while another group remained in the cool greenhouse. The timing and number of flowers produced by the plants in the various treatments were monitored.

As you can see from Table 1, while the vernalization treatments had little effect on, or even delayed the timing of flowering in both cultivars, there was a substantial increase in the number of flowers produced when plants were vernalized 4 weeks or longer (Photo 6) (Photo 7) (Photo 8).

Another issue in the production of Osteospermum is height control. Although recommendations for growth regulators have been published, we have found that, along with promoting flowering, vernalization treatments, and particularly those 6 weeks and longer, also serve as an effective method for producing plants of an acceptable height. Negative DIF after vernalization provides additional growth regulation if desired (Photo 9) (Photo 10) .

During the course of our experiments, we have noted very few disease and insect problems while growing Osteospermum with one exception: thrips. However, we found that our thrips problems could be minimized by following the control program developed by Dr. Dick Lindquist of the OSU Department of Entomology (Ohio Floriculture Vol. 2, No. 3).

Overall, Osteospermum is a relatively easy crop to produce, and we believe it's one that will be a hit with consumers. We suggest that you give Osteospermum a try this year!