1998/99 OSTEOSPERMUM TRIALS

Potted plant growers have known of Osteospermum plants for quite sometime. Recently, new cultivars have been introduced into the market and more cultivars are expected on a regular basis. By talking with several growers, we realized that lack of knowledge about this crop is the norm and probably limits production quantity. Osteospermum has potential as a specialty crop in the Great Lakes area during Fall and Winter because it not only requires cool environments for vernalization but also because these temperatures improve quality. Furthermore, during Fall and Winter, many growers in this part of the country have space available that can be utilized growing osteospermums.

In 1997/98 Dr. Jim Metzger and his graduate student Ayumi Suzuki conducted studies on the vernalization requirement and production management of two Osteospermum cultivars: Lady and Nairobi (see OFA Bulletin No. 828, October 1998). We decided to gain information on the new cultivars that have been (or will be) released. To do so, we conducted the first Osteospermum trials in the greenhouses of our Department.

Rooted cuttings of 16 cultivars were received from the Paul Ecke Ranch in California on November 17 and planted the same day in four inch diameter plastic pots using MetroMix 360 and located in a greenhouse section at 72 F for plant establishment. Fertilizer applied was a 20-10-20, at a rate of 200 ppm Nitrogen three times a week. On December 7, plants were pinched to 5-6 nodes. On December 21, the temperature was lowered to 40 F for vernalization. On January 20, the temperature was increased to 72 F for forcing. On February 26 the majority of cultivars reached peak flowering. Whenever plants were at 72 F, they also received supplemental light from 6:00 AM to 6:00 PM. No growth regulator was applied; this allowed us to distinguish tall from short cultivars.

Some cultivars performed very well under our environmental conditions (Figure 1). Even without growth regulators, the cultivars Brightside, Hihside, and Beira were short enough to be attractive (See Table 1 below). These cultivars also had a large number of flowers with short pedicels. There was a wide range among cultivars in the number of flowers and flower buds, from 40 to 12. There was also variation in flower diameter from 1.7 to 2.8 inches, although the majority of cultivars had flowers 2.4 inches in diameter.

The cultivars were also evaluated on overall quality and appearance by a small number of people (grower, OSU Faculty and Staff) on March 5th. Cultivars were rated using a 1 - 5 scale, being 1=poor and 5=excellent (See Table 2 below). Due to the small number of participants in the evaluation, these ratings should be taken with "a grain of salt".