Your tree might actually thrive by being smaller and growing more slowly. That may sound counter-intuitive, but developing data of  tree growth regulators seem to support that, in urban and suburban areas, smaller trees enjoy better longevity and richer color – and cost less to maintain.

We recently reviewed an article by Tom Prosser, the man behind Cambistat, which is a growth regulator we’ve used over the past ten years. We’ve found the results on target trees to be predictable and economical. But why even use a growth regulator?

Control Growth. Removing a tree is a costly undertaking that can leave a barren spot in your yard. Spruce, elm and cottonwoods quickly outgrow their site and a beloved tree may need to be removed. Using a growth regulator once every three years will control the growth. A growth regulator can limit tree growth up to 60%.

Different tree species differ in their sensitivity. A dogwood may see its one year shoot growth inhibited by 80% while a cottonwood or spruce as little as 20%. Diameter growth of the trunk, branches and large roots will also be reduced along similar proportions. Leaf growth is not as affected although it can cause leaves to be smaller.

Water Detection. A growth regulator can minimize the production of larger roots and increase the fibrous root production making your tree more flexible in its all-points search for water. Tree roots are dominated by larger, woody roots, while the smaller, fibrous roots are underdeveloped as energy drives shooters and suckers into turf.

Cure Root Damage. A tree growth regulator can also help with root chlorosis in situations where the root system is damaged through soil compaction, drought or construction. Beware that a growth regulator like Cambistat could increase fruit production on a fruit tree or sweetgum.

Greener Leaves. Research has shown an increase in leaf thickness and the number of trichomes or leaf hairs produced when using a growth regulator. This can help maintain water balance during drought conditions as well. Researchers think the concentration of chlorophyll is increased causing leaves to be a darker green. Fall color and the leaf drop have not shown to be affected.

How Do Growth Regulators Work

There are two main types of growth regulator. The first type kills tree cells on contact and works like a light herbicide. The second type of growth regulators do not kill tree cells, but limit the elongation of them creating smaller cells and a smaller tree.

Maintaining tree size in this manner can help trees,

  • Steer clear of power lines, buildings and other structure.
  • Reduce the overall cost of trimming.
  • Reduce the use of fertilizer.

In short, the tree could live longer while using fewer resources. Studies indicate that smaller trees

  • Stay healthy.
  • Have a greater degree of root growth.
  • Endure urban stresses better

Brands of growth regulators included Profile 2SC, Cambistat, which is a systemic treatment, and Florel which is directly applied as a foliar spray. We don’t use Florel on apple trees or crabapple trees, because in our tests it hasn’t been effective. We do, however, offer a Cambistat application service for maple and spruce trees, which may grow too large for the space in which they are planted.