Wildlife Photograph

From the Ground Up: Why Exotic Plants are Harmful

Monday April 03, 2006
This monthly article, contributed by Ijams' Park Manager, lends insight into what's really going on at Ijams.

The Tennessee Valley has 358 native trees, shrubs and woody vines.  Forty five additional species have been introduced from around the world.  Many of these introduced plants are invasive, meaning that they escape our yards and displace the native flora.  They are called exotic because they are not indigenous and did not evolve on our continent. Exotic plants invade the natural landscape by various means of dispersal including wind, water, animals that eat the seeds and vegetative growth.  The plants then out-compete native plants as there are no natural controls to keep them in check.  They leaf out earlier and shade the ground at critical periods of wildflower growth.  Others grow very fast and have the advantage to take over a forest or disturbed area. Kudzu vine, for example,  has overgrown entire forests killing everything beneath. Japanese honeysuckle vines spiral around small trees and cut into the bark as the trees grow, causing weak and deformed trunks.  Its leaves cover the top of the tree canopy like an umbrella depriving the tree of sunlight needed for photosynthesis.
Invasive plants also have negative impacts on soil organisms, known as michorrizae, that benefit the growth of tree seedlings and wildflowers. This may cause native flowers and shrubs that provide food, nectar, and shelter to be reduced in number.  Butterflies often rely on particular host plants as their major source of food.  If their host plants are reduced or eliminated, so are the butterflies.                                               
As you walk around the trails at Ijams you may notice that we have been pulling up shrubbery and cutting down trees. You may even see groups of volunteers or park staff using tractors and equipment in the forest.  We do this in order to control the growth of exotics on Ijams grounds.                                                                         
Over the years we have reduced the number of exotics to make room for wildflowers and tree seedlings to grow.   Our hope is that one day, when you visit Ijams, every tree, flower and shrub you see will be a Tennessee native.

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