Response of Conocarpus Trees Growth to Pruning and Paclobutrazol Treatments

This study was conducted at the Educational Farm of the College of Food and Agricultural Sciences – King Saud University in Riyadh area, to investigate the growth response of  Conocarpus  erectcus L.  trees  to pruning and  paclobutrazol treatments. Uniform conocarpus seedlings were transplanted in 40 cm plastic filled with sandy soil, and grown under wooden house. Pruning treatments (50% or 25% of plant height) with or without paclobutrazol at  the rate of 500 or 1000 ppm, and paclobutrazol sprays  at the same rates were used. The plants were sprayed with paclobutrazol twice: immmediately after pruning (when plants were six months), and 3 months later. The experiment layout was Randomized Completely Block Design ( R.C.B.D.). The results showed significant differences in the studied vegetative growth parameters of conocarpus trees among the pruning and paclobutrazol treatments. The 50% pruning with or without paclobutrazol were the most effective treatments in shortening plant height, stem diameter and number of vegetative branches, while the control gave the highest values for these parameters. Leaf area in the 50% pruning with or without 500 ppm paclobutrazol, and in the 25% pruning plus 1000 ppm paclobutrazol treatments was less than in the control where no significant differences in leaf area were found between the other treatments and the control. The results showed that the pruning and paclobutrazol treatments gave lower  fresh  and dry weights of the branches and whole shoots than the control. The 50% pruning plus 500 ppm or 1000 ppm paclobutrazol treatment gave the lowest values for root quality and fresh or dry root weights, while the 500 ppm, 1000 ppm paclobutrazol and the control treatments resulted in high values for these parameters. It is concluded from this experiment that pruning of conocarpus trees especially at the 50% pruning with or without paclobutrazol, helps to decrease their shoot and root growth while the trees remain in acceptable shape.