Seven geranium cultivars that were introduced from Sluis & Groot Co. in Netherland were sown in January, grown in the greenhouse, and treated with foliar applications of 25, 50, and 100ppm of paclobutrazol (PP-333) and 500, 1000, and 2,000ppm of chlormequat (Cycocel, CCC) to determine the growth retarding effects. Among the cultivars, ´Cherie ´80´ was used for another experiment of shade tolerance during hot summer season in Korea. The plants were transferred outdoors and grown under full sun, 20%, 55%, 70%, and 90% shade from June to August. Results are summarized as follows:
1. Of the 7 cultivars, ´Cherie´ 80´ and ´Ringo Rose´ were about 19cm high at anthesis, but the others of white or red flower color were too tall to be used for pot geraniums.
2. Treatment of two growth retardants resulted in reduced stem elongation compared to untreated plants. Chlormequat showed variant effects according to the different cultivars. Regardless of applicated cultivars, paclobutrazol showed sensitive effect according to the concentrations. A concentration of 50ppm paclobutrazol seemed to provide the desired growth response.
3. In shade treatment experiment, the 70% shade increased ornamental value compared with the other shade levels. The plants grown under the 55% shade were a little inferior to those under the 70% shade in growth, but superior in flowering. At the 55∼70% shade levels geranium cultivars seemed to be maintained highly valued in growth and flowering when grown in hot summer.
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