Help Stop the Invasion of Unwanted Trees

We venture into controversial territory with this topic. One problem is that a tree considered as an invasive to one person may be highly valued by another. It is somewhat analogous to “one person’s trash is another person’s treasure.” Another thing that makes this topic difficult is that a tree in its natural habitat most likely is harmless and fills an ecological niche. It is when it is transported outside its natural range that it can become troublesome. 

There is also the challenge of unlearning long-standing information. For example, autumn olive trees (Elaeagnus umbellata) were once touted by college professors and natural resource managers as the thing to plant to help wildlife. They were introduced into the United States around 1830 and were long promoted as a way to improve wildlife habitat and control soil erosion. Unfortunately, this small tree has the ability to create dense shade, crowd out native vegetation, interfere with natural plant succession, and disrupt nutrient cycling. In short, it alters the ecosystem — and not in a beneficial way. 

Still another challenge is that some invasive trees, like invasive insects, have look-alikes that are perfectly harmless and in many cases beneficial. Native sumac species (Rhus spp.) and young walnut trees (Juglans spp.) can easily be confused with the invasive tree of heaven (Ailanthus altissima). Finally, there is sometimes name confusion. For example, the common name goldenraintree is used both with the benign shade tree Koelreuteria paniculata and its invasive cousin, Koelreuteria elegans. 

Vines, too, can be villainous in the landscape. The smothering effects of white bryonia and English ivy are well-known, and the infamous kudzu is said to sometimes grow a foot in a day, covering all in its path. These and other plants require action, too, but we are focused primarily on trees here. 

Despite the daunting challenges, invasive trees warrant the attention of tree boards, urban foresters, and all property owners.