Growth Regulators

Growth Retardants: A Promising Tool for Managing Urban Trees

Trees and shrubs often grow too large for the available space in urban areas. In the past, costly
mechanical trimming was the sole method available to arborists and utility foresters to reduce tree and shrub size. Consequently, chemical growth retardants were developed as an inexpensive approach to limit size and the growth rate of trees and, at the same time, to
enhance their tolerance to the harsh environmental conditions of urban areas. Read more here.

Growth regulators have many benefits in the landscape:

resizedimage600197-Cambistat RTSA-Treated-Leaves-Cambistat (1)Twenty-five years ago, growth regulators were mostly utilized by large utility companies to keep trees out of power lines, but largely ignored by tree health professionals. Today, growth regulators are better understood, widely used, and benefiting trees in ways beyond growth regulation alone, including:

  • Drought Tolerance
  • Greener Leaves
  • Disease Resistance
  • Root Growth

When growth regulators are applied to the root zone of a tree or shrub value can be added by:

  • Extending the time between trimmings, which helps maintain a tree’s size for at least 3 years.
  • Creating healthier trees by increasing root hair growth.
  • Increasing drought tolerance.
  • Redistributing carbohydrates (trees make their own food through photosynthesis) from growth to storage and fine roots.
  • Extending the lifespan of trees by reducing stress from limited root space.
  • Extending the serviceable life of a tree planted too close to a building or utility wires.
  • Correcting mild micronutrient deficiencies.
  • Allows the tree to grow steadily, requiring less pruning and providing added tolerance to certain diseases and insects.


How does is all work?

All trees and shrubs contain a Growth Hormone called Gibberellic Acid or GA for short. GA is principally responsible for cell expansion and to a lesser extent cell division (the process of branch growth). The active ingredient of the growth regulator reduces the effects of GA on the cells. The direct effect is a dramatic reduction in vegetative growth, especially internodal elongation. Which means, the size of treated trees can be effectively regulated by up to 90% for at least 3 years, depending on use conditions. Since many fungi are also affected, treated trees show significantly less effects from a range of plant diseases. Tree growth regulators are applied by calculating the amount of solution required for the specific tree. The specific amount depends on the type and size of the tree. The mixed solution is then poured as a drench around the base of the tree. The active ingredient is then taken up by the roots and distributed to the tree’s growing points, where vegetative growth reduction can be seen. The amount of time for root uptake and distributed to the growing points varies according to soil type, soil conditions, time of year and tree species. The growth control is approximately 40-60%, varying by species. Effective growth control generally lasts for about 3 years and then needs to be re-applied.

Contact Arbor Doctor now to learn how growth regulators can benefit your landscape. You can use our simple online booking calendar to schedule your landscape evaluation now. Please note that some visits have a cost associated with them. Follow up service for current customers is ALWAYS free. Landscape evaluation charges are credited 100% if we perform a service for you.