Green Horizons

In the last issue of Green Horizons we covered two methods of removing unwanted trees from your woodland: felling and girdling. We will conclude this topic by looking at frilling, tree injection, basal bark spray, and cut stump application.

Frilling
Frilling is a variation of girdling in which a series of downward angled cuts are made completely around the tree, leaving the partially severed bark and wood attached at the bottom (See Figure 1, pg 3). Frilling is done with an ax or hatchet. One needs to be especially careful when frilling hardwood trees like ironwood or maple because of the ax’s tendency to glance-off this extremely dense wood. For that reason alone, I do not like this method. Besides, it tends to be a time-waster.

Figure 1: Frilling, in which downward angled cuts are made completely around the tree, is timeconsuming and potentially dangerous in densewooded species like sugar maple.

Figure 2: The tree injection method involves making spaced cuts around the trunk and applying a water-soluble herbicide directly in the cut.

Tree Injection – Spaced Cuts
Tree injection involves introducing a herbicide into the undesirable tree through spaced cuts made around the tree’s trunk with an ax, hatchet, or tree injector (Figure 2). Non-overlapping horizontal cuts penetrating into the sapwood (the outer area of lighter-colored wood in the stem cross section) are made completely around the tree. Cuts are approximately 2 inches long and are spaced with their edges 1 to 3 inches apart, depending on tree species and specific herbicide being used.

As the cut is made, open the wound with the ax blade and allow 1 to 2 milliliters of the chemical to run down the blade and into the cut. This is a very small quantity; but fortunately, most quart spray bottles deliver this amount.

Figure 3: With the basal bark spray method, the herbicide is applied to the lower 12"-18" of the trunk of trees less than 4" dbh (diameter at breast height).

Figure 4: With water-based herbicides, you only need to treat the sapwood and bark of the cut surface of the stump.

Basal Bark Spray
Basal spraying, or basal bark as it is sometimes referred to, is a technique to deaden small trees, shrubs, and occasionally vines by spraying the lower 12 to 18 inches of the trunk with a herbicide (Figure 3). The intent is for the herbicide to penetrate the bark and kill the tree and any basal buds that might sprout.

Herbicides used for basal spraying are generally applied in oil carriers. The technique is effective on trees less than 4 inches in diameter. One clear advantage of this technique is that because it is typically used with oil-based herbicides, it can be done during spring sap flow. One disadvantage, however, is that as bark becomes rougher and thicker, the technique becomes less effective.

Care must be taken when the herbicide is applied to minimize the amount that runs into the soil. This is important not only from an environmental quality standpoint, but also to avoid damaging non-target trees. The roots of trees often extend well out beyond their crowns. It would not be at all unusual for the roots of an adjacent desirable tree to extend below the trunk of a tree being basal sprayed. If excess amounts of herbicide were applied to the treated tree, the adjacent desirable tree could absorb the herbicide and be killed or seriously damaged.

Cut Stump
When a tree or vine is cut, there is a high probability that the stump will sprout. Sprouting can be eliminated by treating the cut stump with a herbicide. The herbicide can be applied to the stump in many ways; the most common being to spray with a backpack or hand-held sprayer.

How much of the stump needs to be treated depends on the formulation of the herbicide. Many herbicides labeled for cut stump application are water soluble. The critical area of the stump that must be treated to prevent sprouting is the sapwood and bark of the stump’s surface (Figure 4). Stump treatment with water soluble herbicides must be done immediately after cutting to be effective. If treatment is delayed, adequate downward movement of the herbicide will not occur and sprouting will not be eliminated.

Figure 5: With oil-based herbicides, spray the entire stump, particularly the exposed roots.

Some herbicides labeled for cut stump application are to be mixed with oil. These materials do not move readily in the plant, but penetrate the bark. To be effective, the entire stump, particularly the bark and exposed roots must be thoroughly sprayed (Figure 5). Timing is less critical because these herbicides are not so dependent on downward movement from the cut surface for distribution. In situations where immediate treatment of stumps is not possible, an oil-based herbicide should be used rather than a water-soluble formulation.

Treatment with an oil-carried herbicide is also recommended in the spring when treating species that have a strong spring sap flow such as maple, grape and ironwood. Water-carried herbicides will usually not be adequately absorbed to be effective during this time of year.

Specific Herbicide Recommendations
An excellent reference for specific herbicide rates based on application technique entitled, “Herbicides Commonly Used for Controlling Undesirable Trees, Shrubs, and Vines in Your Woodland”, is available online from Ohio State University Extension at http://ohioline.osu.edu/for-fact/index.html. As always, remember to READ THE ENTIRE LABEL before using any herbicide.