Landowners often only allow contractors to cut tree growth back to the minimimum distance required by legislation; this results in costly annual maintenance visits. It may be possible to overcome this by the use of tree growth regulators which retard tree growth.
ADAS in association with Bartlett Tree Research Laboratories are currently undertaking trials on behalf of five of the UK electricity distributors (Central Networks, EDF Energy, Scottish & Southern, CE Electric and WPD) investigating the effectiveness of using a tree growth regulator to control vegetation growth. This is widely used by electricity distributors in the United States and Canada but to date has not been used in the UK.
The tree growth regulator is injected into the soil around the base of the tree and is drawn up into the tree. The effect of the tree growth regulator is to inhibit extension growth, reducing biomass production above ground, without adversely affecting the shape and visual amenity that the tree provides. Indeed it provides positive benefits to the tree through increased fine root production and can confer resistance to some vascular wilt diseases and increases the tree's tolerance to drought.
Six woodland sites have been selected throughout the UK and a range of the quicker growing tree species (including ash, sycamore, poplar, lime, leylandii, hawthorn, silver birch, alder and willow) selected for treatment.
An equivalent number of trees at each site also form part of the trial but are not treated and act as a control comparison against the treated trees.
All of the six sites were treated in Summer 2009 and the sites will be assessed over the next five years for growth; leaf colour; size and fine root growth; chlorophyll fluorescence; fine root density and any potential adverse effects of being treated with the tree growth regulator.
It is anticipated that the project will show that treatment with tree growth regulator is a safe and effective method for controlling tree growth close to overhead lines. Trees that would normally require annual pruning will instead, following treatment, only require pruning every four to five years. For landowners this method may also, in many cases, be a more visually sympathetic solution to controlling tree growth than regular pruning.
The project is a collaboration between ADAS and Bartlett Tree Research Laboratories with support from Syngenta. For further information contact the project manager Mark Walkinton on 01924 848520 or e-mail mark.walkinton@adas.co.uk
