Results of Treatment:
The growth control creates physiological benefits that help trees & woody shrubs withstand urban stresses, such as poor soil, limited root space, & drought (Watson 1996, Chaney 2005). Woody shrubs can be controlled for roughly (1-2) years and shrubs show approximately 90% growth control. Other benefits include increased root hair growth and darker, healthier green foliage.
Rules for Application of ShortStop TGR:
Calculating the volume needed for woody shrubs is different compared to trees: instead of using dbh, the “shrub crown” volume is calculated (LxWxH) and does not include the lower exposed stem/trunk (Mann 2008). Shrubs are rate specific and PGMS has rates for over fifteen woody shrubs. Some of the shrubs included on the list are arborvitae, boxwood, burning bush, and Viburnums. In many southern states, Dogwood is considered a woody shrub, but the tree rate and application procedure should be used for all Dogwoods (PGMS’ refined rate only). The opposite is true for Yews and Junipers; the woody shrub rate and application procedure should be used.
REFERENCES:
Chaney, W.R. 2005 Growth Retardants: A Promising Tool for Managing Urban Trees, FNR-252-W Purdue Extension Publications.
Mann, L.A. 2008 Provide a New Service: Controlling the Growth of Woody Shrubs & Trees, GreenSmart: a Newsletter for Arborists First Quarter.
Tabbed Arborist Worksheets: Shrub Instructions and Shrub Rates 1&2 © Plant Growth Management Systems, 2004
Watson, G., 1996. Tree Root System Enhancement with Paclobutrazol, JOA, 22(5):211-217.
Real Examples of Real Applications:
Burning Bush (genus- Euonymus) – Central Indiana
TreeMasters’ client felt their burning bush was crowding against the house and requested a TGR application in March 2008. Jeff Ling of TreeMasters observed that the growth control was more than 50% during the two seasons following application and the client was pleased with the noticeable decline in the shrub’s growth.
Yews (genus- Taxus) – Northern Illinois
In October 2006, Chuck Vostry of Vostry Tree Care treated three yew plants. The total shrub volume was 756 ft3 (9 ft x 14 ft x 6 ft) and the application was completed by trenching around the base of each plant. Prior to the treatment, it was necessary to trim the yews twice a year. Since the treatment, no trimming has been necessary, except a little off the top, and the yews look denser and healthier. Chuck was pleased to see growth control lasted for three seasons which may be due to being in the northern part of the U.S.
Privet Hedge (genus- Ligustrum) – East Tennessee
A privet hedge the size of 400 ft3 was pruned and treated in April of 2009 by Tom Perry of Cortese Tree Specialists, Inc. Soon after application, no growth was observed during the following two years, except for a few “wild-hair” branches. Tom was quoted to say “We use ShortStop TGR every chance we get. Whenever there is privet, Holly, Bradford Pear, or other very fast growing hedge or tree. The TGR stops the growth!”
Lilac (genus- Syringa) – Northern Indiana
Walt Kanoff of Envirovision Inc. “abhors power-shear-everything type of pruning,” and treated six (6) similarly-sized Dwarf Lilacs in late June, 2008 by soil injection. The application was only around the outside of the stem clusters, but there was significant open area within the stem clusters (possibly causing unequal distribution). He got varied results which may have been due plant individuality and uneven distribution. He will not be discouraged and intends to make future applications at recommended rates, but will increase the area of application to the root zone within the plant stem clusters, as well as outside of the stem clusters.
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