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Special Opportunities for Utilizing TGR Applications

There are special situations where ShortStop® Tree Growth Regulator works exceptionally well.
Woody Shrub growth can be easily controlled using TGRs and the shrubs look great following an application. The overall profitability (ROI) is greater using TGR applications to control woody shrubs when compared to all the costs involved in repeat trimming (Burch et al. 1996), especially with clients that have an annual contract. 

Combining TGR applications with other remedial treatments creates therapeutic advantages that many treatments cannot produce alone. Chlorosis Remediation and Assisting Newly Planted Trees are perfect examples of situations where this “synergy” is evident.


Results of Treatment, Rules for TGR Application, and Real People Examples

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.

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.

Recommended application procedure is sub-soil; either basal drench or soil injection. Foliar spray applications are not recommended because they have a limited application window, leaf residue, increased chance of off- target accidents, short length of control, and poor control due to incomplete coverage.

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.

Sample application time/cost illustration for a Viburnum;


The symptom, Chlorosis (yellowing leaves), can be greatly reduced by ShortStop TGR treatments and soil supplements. The newly generated root hairs (min. 2 years) can help the tree’s resilience. In some cases, soil supplements become unnecessary by the third year following an application of paclobutrazol.

Using paclobutrazol to reduce or eliminate chlorosis is dependent upon two factors: the size of the tree (dbh) and the level of leaf discoloration (yellowing). As the size of the tree increases, the amount of yellowing must be less and less extreme, to expect a recovery using TGRs. In larger trees, (20” dbh and greater), the application is not likely to help trees that are very chlorotic. This may be due to excessive vascular damage that prevents materials reaching the canopy effectively. 

Long-term versus Short-term Solutions
Adding soil supplements to trees showing chlorosis helps them look greener but it is really just treating the symptoms, not the underlying problem. Many chlorotic trees do not have an adequate root system, so the trees are unable to utilize the fertilizers or supplements that otherwise would be available. The long-term solution is to build a better root system, which is achieved using ShortStop TGR and giving the tree at least two years to create the newer root hairs. During this time, the applicator can continue to add the fertilizers or supplements for the greening effect. For the best results, pair up TGR treatments with basic, low-salt fertilizers or plant/food nutrients during the 2-3 years following the TGR application.


The best way to protect your investment in the planting and maintenance of new trees is to utilize ShortStop TGR. Whether at the time of transplanting or recently planted and struggling to get established, trees are directly facilitated by a TGR during these stressful times. Paclobutrazol, the active ingredient in ShortStop TGR, enhances the tree’s ability to survive the establishment phase of planting and promotes the growth of root hairs. Other physiological changes; smaller stomata, more leaf hairs, and thicker cutin make the transition easier for the trees. It is important to know that the TGR rate amounts can vary greatly between the three different types of trees: mature or midlife, juvenile, and small or young.

Call us #269-663-7467 for more information about assisting newly planted trees -not only to survive, but to thrive with a modified application of ShortStop TGR.