Tom Hughes, director of research and science for the NWTF, says a number of trees make good candidates for two habitat improvement tools: hack-and-squirt and girdling.
It’s ideal to remove trees such as sweet gum, maple, elms, ashes, poplars or other undesirables when they are competing with trees that have better mast production for a variety of wildlife. The methods can also be used on invasive plants such as the ailanthus.
Removal method will be determined by the kind of tree being removed. The ailanthus, if cut down or girdled will send out new growth away from the cut or girdled area making the hack-and-squirt the method of choice for this species. Conversely, girdling is probably a better way to eliminate a red cedar when it is growing among a stand of young oaks.
When land managers girdle a tree, Hughes stresses that they should take care that their chainsaw cuts deep enough into the cambium layer (the growing part of the tree beneath the outer and inner barks) so that the tree begins to die — something that many folks fail to do. Bob Boeren, who operates Boeren’s Forestry Consulting Service, agrees with Hughes and explains how to correctly girdle.
“Begin the cut at a height comfortable for you, such as at the waist,” he says. “Make sure the bar enters (a quarter of the way) through the tree, enough to cut through the bark and well into the cambium. Cut all the way around the tree in a circle, so that where you finish is where you started; in other words, in a complete circle so as to not to leave a gap. This will ensure the tree will start to die.”
The forester says that he often makes two such cuts, just to make sure. Boeren adds that a girdled tree will often stand for several years, while becoming a source of insects for woodpeckers and other birds and occasionally becoming a den tree for various wildlife species. A land manager can later level the tree or allow it to fall on its own.
Hughes believes landowners sometimes commit several mistakes when using the hack-and-squirt method. First, they do not inject the solution deep enough into the tree for it to attain good penetration; second, they either use too much or too little solution. Also, particularly in the case of the former, nearby trees receive collateral damage from the solution being sloshed over them or ground transfer occurs and kills a desirable tree from the roots.
At chest height, Boeren uses a hatchet as the hack part of this technique. He makes three or four cuts for an average size tree (more for larger trees), each deep enough to expose the cambium and form a cup that holds an herbicide. Then, using a regular plastic spray bottle, he squirts the herbicide solution into each cut. An herbicide from the Garlon family is one of many options to use.
Both girdling and hack-and-squirt can be done throughout the year, but for the latter, avoid doing it when the sap is rising, as it can wash the herbicide out of the cup. You may well find that girdling and hack-and-squirt are two of the simplest and most effective ways to manage a forest.