GROWTH REGULATION OF LARGE-FLOWERED RHODODENDRONS (RHODODENDRON X CATAWBIENSE MICHX.)
Traditionally, large-flowered Rhododendrons are garden plants. However, in view of their large blooms, they also offer good prospects as flowering potted plants. Many cultivars properly develop buds only after the third pinching operation though. At that time, the plants are already too big to keep them indoor. Plants of the large-flowered Rhododendron cultivar 'Albert Schweitzer' have been sprayed at different times on the leaves with a concentration of paclobutrazol of 200 mg/l shortly after the second pinching. All plants tested showed a strong inhibition of their upward growth. Bud formation was stimulated and was better the shorter the application with paclobutrazol had been after the second pinching operation, within one week. Certain lots were treated twice. Double application produces even more flowers. Hence, paclobutrazol makes it possible to produce large-flowered Rhododendrons as indoor plants.
MERTENS, M. (1994). GROWTH REGULATION OF LARGE-FLOWERED RHODODENDRONS (RHODODENDRON X CATAWBIENSE MICHX.). Acta Hortic. 364, 127-130