Controlling volunteer trees

Trees are a vital part of every landscape, they provide the ‘ceiling’ for every outdoor room.  But there are certain trees that are very good at reproducing themselves by reseeding in nearby planting beds, around fences and other out of the way places.  Here are some tips to consider in order to get control over these unwanted volunteer trees.

Is it desirable?

The first question to ask is if the unwanted tree is desirable or not.  If the tree is still small and a desirable species such as oak, you may want to consider transplanting it in the spring if you have a space in the landscape for such a tree.   But many trees that reproduce profusely are not desirable enough to transplant or save.  Trees such as Siberian elm, silver maple, hackberry, tree of heaven, mulberry and other ‘weedy’ trees are not trees we care to transplant.

Cutting isn’t enough

Most, but not all, trees resprout after cutting. Cutting those that don’t resprout is an effective control method. For example, eastern red cedar is a very common species that will not resprout after being cut off at ground level.   Trees that do resprout include Siberian elm, hackberry, Osage orange (hedge), oak, ash, aspen, cottonwood, maple, sycamore, willow and many more. These trees will either need to be dug out or have the cut stump treated with herbicide after cutting to ensure no regrowth.

A note of caution

Note that when we say volunteer trees, we mean those that grow from seed rather than suckers (trees that grow from the roots of an existing tree.) The recommendations given in the remainder of this article are designed to kill volunteer trees that grow from seed. Using herbicides on suckers will damage and very possibly kill the original tree. Trees that commonly produce suckers include tree of heaven, honeylocust, black locust, hackberry, western soapberry, cottonwood, aspen, poplar, willow and boxelder.

It is also possible for larger trees of the same species to be root-grafted.   Even though root-grafted trees are not suckers, they do share materials between the individual root systems and therefore herbicides used to treat one tree can be passed to its neighbor.  Be sure the volunteer tree you are treating is not large enough to be root grafted to a nearby tree of the same variety or a sucker off of another desirable tree in the landscape.

Herbicides available

Triclopyr and glyphosate are the herbicides recommended for volunteer tree control. Triclopyr is found in many brush killers and glyphosate is found in Roundup as well as numerous other products. Read the label before purchasing to make sure that a cut stump treatment is listed.

Most often the undiluted product is applied to the stump immediately after cutting. A paint brush is often used for the application.  It is important that the stump is treated immediately or at least within 5 minutes of cutting. Note that a paint brush with foam rather than bristles is less likely to drip.  Trees do not need to be actively growing to be controlled. Actually this time of year is a very good time to treat as long as applications are made when the temperature is above freezing.