1. This document is ENH 130, one of a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. First printed October 1987. Reviewed February 1999. Please visit the FAIRS Web site at http://hammock.ifas.ufl.edu. The Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information and other services only to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension Service office. Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / Christine Taylor Waddill, Dean 2. Gary W. Knox, Associate Professor, North Florida REC, Monticello, and Jeffery G. Norcini, Associate Professor, North Florida REC, Monticello, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, 32611. The use of trade names in this publication is solely for the purpose of providing specific information. It is not a guarantee or warranty of the products named, and does not signify that they are approved to the exclusion of others of suitable composition. ENH 130 Effects of XE-1019 and Pruning on Pyracantha koidzumi Wonderberry, Photinia x fraseri, and Ligustrum x ibolium 1 Gary W. Knox and Jeffery G. Norcini 2 NATURE OF WORK There is a growing interest in the use of plant growth regulators on woody ornamentals to reduce vegetative growth and the frequency of pruning. Plant growth regulators are already used by utility companies as a cost-effective means of controlling tree growth around power lines (2, 3, 4). Chemical control of vegetative growth may prove to be a cost-saving alternative to pruning in nurseries as well. XE-1019, an experimental growth regulator to be marketed as Sumagic (Chevron Chemical Company), effectively controls plant height in poinsettias, chrysanthemums, and several bedding plants (1, 5). It will soon be labeled for use on these species; testing is currently underway for its use on woody ornamentals. The purpose of this study was to evaluate XE-1019 as an alternative to pruning on three fast-growing woody ornamentals. Pyracantha koidzumi Wonderberry, Photinia x fraseri, and Ligustrum x ibolium were grown in pine bark:Canadian peat:sand, 2:1:1, in l-gallon containers. On September 19, 1986 the plants were pruned and 3.4 oz XE-1019 applied as a soil drench at a concentration of 25, 50, or 100 ppm. Plant height and width, recorded on September 19, 1986 and April 13, 1987, were used to calculate the growth index (height + width /2). Table 1. Effect of XE-1019 on the change in overall size. XE-1019 Drench (ppm) Change in Growth Index 1 after 7 months Pyracantha Photinia Ligustrum 0 18.0 a12.6 a 9.6 a 25 10.6 b 6.7 b6.2 b 50 8.4 bc 6.3 b5.5 b 100 7.1 c 5.9 b5.2 b 1 Growth Index = [height (in.) + width (in.)]/2; values with different letters within a species are significantly different at the 95% confidence level. Drenches of XE-1019 at 25, 50, and 100 ppm equally decreased the overall growth rate of all three species except Pyracantha (Table 1). The growth rate of Pyracantha was decreased slightly more by a 100 ppm drench than a 25 ppm drench.
Effects of XE-1019 and Pruning on Pyracantha koidzumi Wonderberry, Photinia x fraseri, and Ligustr Page 2 February 1999 XE-1019 was a significant factor in reducing the overall size of all three species as well (Table 2). At the three rates tested, XE-1019-treated plants remained small after 7 months unlike the untreated pruned and unpruned plants which both grew to about the same size. However, pruning proved to be the best method for obtaining a desirable habit of growth with Pyracantha, Photinia, and Ligustrum. LITERATURE CITED Barrett, J. E. and Terril A. Nell. 1986. Evaluation of XE-1019 and paclobutrazol for height control of flowering annuals. Proc. Plant Growth Reg. Soc. Amer. 13:62-64. Bowles, Howard. 1985. Growth retardant use by utility companies. J. Arboric. 11:59-60. Ulrich, Erich S. 1987. Utility line clearance in our urban forests. J. Arboric. 13:62-64. Watson, M. R. 1987. Use of tree growth regulators at Potomac Edison. J. Arboric. 13:65-69. Wilfret, Gary J. 1986. Growth retardation of chrysanthemum and poinsettia with Ortho XE-1019. Proc. Plant Growth Reg. Soc. Amer. 13:65. Table 2. Effects of XE-1019 and pruning on overall size of Pyracantha koidzumi Wonderberry, Photinia x fraseri, and Ligustrum x ibolium. Treatments Growth Index 1 7 Months after Treatment XE-1019 Drench (ppm) Pruning 2 Pyracantha Photinia Ligustrum 0 No 28.6+/-1.7 27.0+/-0.9 21.3+/-1.0 25 No 23.4+/-2.0 22.9+/-1.0 18.4+/-0.9 50 No 21.5+/-1.9 20.7+/-0.7 16.7+/-1.1 100 No 19.1+/-1.2 21.1+/-0.6 16.8+/-1.1 0 Yes 29.8+/-1.5 21.7+/-1.2 16.9+/-0.6 25 Yes 20.7+/-2.3 14.7+/-0.6 12.2+/-0.3 50 Yes 16.5+/-1.2 15.1+/-0.5 11.5+/-0.4 100 Yes 14.5+/-0.9 15.2+/-0.7 11.2+/-0.4 1 Values represent the growth index +/the standard error of the mean; growth index = [height (in.) + width (in.)]/2. 2 Performed at the time of XE-1019 application.