Regulating or Controlling Tree Growth
Trees in suburban yards often outgrow their space and become a nuisance. In some instances heavy pruning takes place which complicates other issues of regrowth and wounds. Paclobutrazol can slow growth up to 70%, imagine that a tree would naturally grow 100cm in a year, with an application of Paclobutrazol it may only grow 30cm. In addition it has many other benefits such as increasing hairy root mass, thicker darker leaves which resist pest and environmental stressors such as drought, and it has fungicidal capabilities which helps older trees especially.
For over 30 years the agricultural and turf (golf) industries have known of and used PACLOBUTRAZOL to control vegetation growth. The product also encourages flowering and it is also used to bring about unified timing of flowering of crops for pollination. There's more information in this PDF about Paclobutrazol and it's use with trees.
Product usage in Australia is governed by the label on the product. Labels are acquired via APVMA and deviation from the label is disallowed unless a permit is acquired.
I have secured the APVMA permit to apply PACLOBUTRAZOL to a selected range of trees.
How is PACLOBUTRAZOL applied?
The product is mixed with water according to the permit/label for the size fo the tree and applied to a shallow trench around the base of the tree, the practice is known as a collar drench. Experience of the arborist is required to fine tune the dosage based on the tree's vitality and vigour, a declining tree with less leaves will required an adjusted dosage.
When is PACLOBUTRAZOL applied?
It can be applied anytime however it is prudent to apply it at the beginning of the growing season when the tree is leaved out (if tree is deciduous). Of course it cannot be applied if the soil is frozen or there's snow etc.
Trees that can be treated
- Eucalyptus Species
- Cadagi (E. torelliana)
- Tallow wood (E. microcorys)
- Tasmanian Blue Gum (E.globulus)
- Peppermit Gum (E. nichollii or E.odorata)
- S A Blue Gum (E. leucoxylon)
- Qld Brush Box (Tristania conferta)
- Poinciana
- Mango
- English Oak
- Ficus spp.
- Leopard Tree
- Melaleuca spp.
- Jacaranda
- Tipuana
- Silky Oak (Grevillia robusta)
- Bottle Trees (Brachychiton spp.)
- English Elm
Other Species




