Early treatment of ornamental plants with retarding substances

Through the use of retardants on mother plants, unrooted and rooted cuttings attempts have been made in this early stage of cultivation to achieve sufficient growth inhibition lasting the entire cultivation period of some potted ornamental plants which otherwise tend to grow too high. Experiments were carried out between April and September on Hibiscus rosa - sinensis L., Chrysanthemum - Indicum - Hybrids (C. x hortorum L. H. Bailey) and Euphorbia pulcherrima Willd. using the retarding angents B-Nine, Phosfon D, Cycocel (CCC) and Alden (piproctanylium bromide). Treatment of hibiscus mother plants with 125 ppm CCC at 6 week intervals was sufficient to influence the next generation as desired. At the same time cutting production was severely reduced. Treatment of chrysanthemum mother plants with B-Nine and poinsettia mother plants with CCC did not yield noteworthy results besides a decrease in cutting production. Prerequisite for the treatment of cuttings with inhibitor is that they have not already developed too long internodia on the mother plants. By standing the unrooted chyrsanthemum cutting stems in 10 or 15 per cent B-Nine solution for 24 hrs, growth of the potted plants was retarded until the end of cultivation. Spray treatments during rooting with 10 or 15 per cent B-Nine on the 10th day after propagation and with 3000 or 5000 ppm Alden on the 8th or 12th day were partly more effective, the high B-Nine concentration led to leaf edge damage. Addition of 500 or 750 g Phosfon D/m('3) to the propagation substrate in conjunction with B-Nine sprayings on the 10th day did not lead to remarkable increased growth inhibition. Influence of early retardant treatments on leaf, shoot and flower number and date of bloom are described. Reduced number of flowers and delayed bloom are noted as disadvantages. The use of CCC on poinsettia cuttings has not yielded satisfactory results. Conclusions are drawn from results of research thus far. Further treatment methods as well as how to proceed on these problems in the future are discussed