ShortStop 2 SC is the newest Paclobutrazol Tree Growth Regulator (TGR) that contains smaller, more uniform particles associated with the 98% purity of the active ingredient.  When applied to roots around the trunk of the tree, ShortStop can:

All plants and fungi contain a Growth Hormone called Gibberellic Acid (GA).  GA is principally responsible for cell expansion and to a lesser extent cell division in juvenile tissue.  The active ingredient, Paclobutrazol, inhibits a cytochrome P450 catalysed step in the biosynthesis of GA.  The direct effect is a dramatic reduction in vegetative growth, especially internode elongation.  Therefore, the size of treated trees can be effectively regulated by up to 90% for 3-8 years, depending on use conditions.  Since many fungi are also affected, treated trees show significantly less effects from a range of plant diseases.

The tree growth hormone called Gibberellic Acid (GA) is produced in actively, newly growing tips which include shoots and roots.  ShortStop 2 SC TGR is applied around the base of the tree and uptake occurs through established roots.  Following uptake, Paclobutrazol only translocates in xylem tissues that are related to upward movement of water and nutrients.  Since the active ingredient can only move upwards, it can only affect above ground GA production.  This results in no effect on root tips and maximum effect on shoot tips.

The end result of the uptake and translocation pattern is a dramatic alteration in what is termed the root:shoot ratio.  Energy produced by photosynthesis in the leaves cannot be used by the shoots and is shifted by the tree into the newly developing roots.  The shift in energy resources results in development of new fibrous roots and enhancement of existing roots.  The enhanced root development dramatically results in increased drought tolerance and increased nutrient uptake, which produce a darker green and healthier tree.  A few of the tree slides compare the darker green trees to the yellower untreated trees.  This effect is particularly important on trees growing in lawns and urban locations with poor root:shoot ratios.

ShortStop TGR is generally applied by applying a calculated amount solution around the base of the tree.  The specific amount depends on the type and size of the tree.  Active ingredient is then taken up by the roots and translocated to the tree's growing points, where vegetative growth reduction can be seen.

The amount of time for root uptake and translocation to the growing points varies according to soil type, soil conditions, time of year and tree species.  The growth control is approximately 50% in the first year and as much as 90% the following years.  Effective growth control generally lasts for about 3 years.  However, if product is reapplied on a regular basis, growth control will remain at approximately 90%.

Due to the reduction in vegetative growth and a build up of chemical reserves, trees generally produce more flowers and fruits.  Although this effect is very important in approved Fruit Production Markets, it does not appear to be significant in shade trees.  However, it is likely that some species may show enhanced reproductive structures and associated seed production.  Some of these effects can be seen in the tree slide show.