Arboriculture & Urban Forestry 36(5): September 2010 Arboriculture & Urban Forestry 2010. 36(5): 221–223 221 Effects of Paclobutrazol on Royal Palm (Roystonea regia) Trunk and Height Growth A.D. Ali and Shawn C. Bernick Abstract. Paclobturazol is a plant growth regulator which reduces cell elongation and growth. It is commonly used in reducing the growth of herbaceous plants and woody dicots. It has also shown activity against young palms, such as oil and date palms. The effects of bas- al drench treatments applied annually or as a single application on mature Royal palms (Roystonea regia) were studied over a three-year pe- riod. No significant effects were noted on lateral trunk growth. Paclobutrazol treatments resulted in slower vertical growth than in palms not receiving a treatment. However, even at 36 MAT, the average reduction in vertical growth (approx. 50 cm) was still not horticultur- ally significant relative to the overall palm height of approximately 7 m. Royal palms may attain heights up to 24 m when mature. It is recom- mended that they not be planted within 7 m of utility lines especially considering regulating their vertical growth is not a practical option. Key Words. Growth; Growth Regulators; Height Control; Paclobturazol; Royal Palm; Roystonea regia. The Royal palm (Roystonea regia) is a valued specimen in Flori- da, U.S. landscapes. Part of their appeal is the smooth, grey trunk topped by a glossy green crown shaft and a dark green canopy con- sisting of feathery fronds up to 3.3 m long. This stately palm can grow quickly under the appropriate conditions of sun, soil mois- ture, and fertility, and reach heights of 24 m. Occasionally, these palms may be found near or growing under utility lines. Slow- ing their vertical growth rate is desirable in those circumstances. Paclobutrazol is a plant growth regulator which in- hibits gibberellin synthesis in apical meristematic tissue, thus reducing cell elongation and growth (Blaedow 2003). This growth regulator has been available for decades and is com- monly used in floriculture as well as in reducing growth of various woody dicots (Barrett and Nell 1983; Ruter 1994; Bai et al. 2004; Watson 2006). Paclobutrazol has been investigated for reducing plant growth near utility lines and in Rights-of-Way as well, in order to minimize power interruptions (Bowles 1985). Various applica- tion methods have been reported including foliar treatment, bark banding, trunk injection, and basal soil drench (Tamsberg 1990). Carvajal et al. (1998) showed that paclobutrazol reduc- es height, rachis length, and leaf area when applied as a soil drench to nursery stock oil palm (Elaeis sp.). El-Hodairi et al. (1998) evaluated paclobutrazol effects on the date palm (Phoe- nix dactylifera). They showed that sequential crown drenches directed at the growing bud at 30 day intervals, reduced tree height in thee-year-old date palms. Hensley and Yogi (1996) investigated the effects of paclobutrazol on selected tropi- cal species. They reported reduced height growth as a result of basal soil drench in Queen palm (Syagrus romanzoffiana) and Manila palm (Adonidia merrillii), 11 months after treatment. The effects of other growth regulators on palms have also been reported by various researchers. Broschat and Donselman (1986) found monthly sprays of Ethephon retarded elongation and re- duced the incidence of flowering in one-year-old Chamaedorea seifrizii. Similarly, Fisher (1980) reported leaf size reduction with Ethephon sprays or leaf tip treatments in young Caryota, Chamae- dorea, Chrysalidocarpus, Phoenix, and Rhapis. Fisher and Theo- bald (1989) evaluated long-term effects of trunk injection with gibberellin or cytokinin in mature coconut trees. Neither product induced vegetative proliferation intended for mass propagation of coconuts. The multi-year study reported herein was conducted to evaluate the effects of paclobutrazol on mature Royal palms. MATERIALS AND METHODS Mature palms growing in a well-maintained landscape set- ting in Naples, FL, were selected for this study. The palms were approximately 7 m tall with an average diameter at breast height (DBH), 1.4 m above ground level, of 38 cm. Soil texture was sandy with pH 7.2 and 3.2% organic mat- ter. Paclobutrazol (Cambistat® 2SC, Rainbow Treecare Sci- entific Advancements, Minnetonka, MN) treatments were as follows: 1) Cambistat 2SC at 1.6 gm ai/cm trunk DBH basal soil drench applied once on February 6, 2007; 2) Cambistat 2SC at 1.6 gm ai/cm trunk DBH basal soil drench applied annually on February 6, 2007; February 5, 2008; and Febru- ary 6, 2009; 3) Untreated Check not receiving any treatment. Paclobutrazol was mixed according to label instructions, and treatments were applied as a basal drench with a water- ing can. Drench volume was 7.6 L/tree. Mulch (pine needles) at the bases of palms were pulled back prior to drench ap- plication then replaced afterwards. The trees were fertilized three times per year with 103 gm each of a granular, slow- release nitrogen fertilizer (7-2-14), applied near the base. ©2010 International Society of Arboriculture
September 2010
| Title Name |
Pages |
Delete |
Url |
| Empty |
Ai generated response may be inaccurate.
Search Text Block
Page #page_num
#doc_title
Hi $receivername|$receiveremail,
$sendername|$senderemail wrote these comments for you:
$message
$sendername|$senderemail would like for you to view the following digital edition.
Please click on the page below to be directed to the digital edition:
$thumbnail$pagenum
$link$pagenum
Your form submission was a success.
Downloading PDF
Generating your PDF, please wait...
This process might take longer please wait
