Controlling Invasive Species in your Forest

Home >> Content >> Controlling Invasive Species in your Forest
John M. Randall, The Nature Conservancy, Bugwood.org

We do a lot of work on our family forest to mold it into the shape and constituents that we most desire.  Needless to say, we have invested a great deal of thought, effort, and resources in our labor of love to achieve our goals.

Often we have encountered setbacks or obstacles that we have had to overcome.  These include wind and ice storms, diseases, and the occasional livestock that has wandered into our forest.  We expect these kinds of events and have built some flexibility into our plans and work to account for these.

However, there are some things that worry us enough to create a whole new strategy for dealing with them.  These are the invasive, non-native plants that are moving around the region and changing the nature our forests.  We have seen the impacts a full-fledged infestation of some of these can have, and very much want to avoid that kind of situation.

So we have become knowledgeable and vigilant when it comes to invasive plants.  We have learned to identify some of the worst ones (like common buckthorn, the non-native honeysuckles, and garlic mustard), and are constantly keeping a look out for these anytime we are in the woods.  We even keep an eye on our neighbor’s property to head off possible nearby seed sources.

When we do find a new infestation on our property, we take quick actions to control the spread and hopefully eliminate the plants.  These include pulling, cutting, and spraying with an herbicide.  Sometimes we utilize a combination of these to increase the effectiveness of our efforts.

Pulling plants can be an excellent method of control.  It is especially effective when the plants are young and the infestation is small and just started and the plants haven’t flowered or produced seed yet.  Older infestations (where the plants have matured and dropped their seeds for several years) can be tackled with pulling, but you can create great conditions for seed germination of the plants you are trying to get rid of.  Pulling plants loosens soil in a way that makes seed germination more successful.

Cutting (or mowing) plants has its benefits and drawbacks.  Cutting is easier to accomplish than pulling since you can use machines (weed whackers and brush hogs) to do the work.  However, some of these plants will readily resprout from cut stems and all your cutting will only slow them down slightly.  Cutting can also have the downside of spreading the plants even further if you cut when the seeds are mature.

Getting rid of the stuff you cut or pull is the next problem.  You have to be careful if either composting or burning the plants as the seeds may survive or you may disperse them further.  If you have cut or pulled them before they have produced flowers then you may be ok in burning or composting.  Otherwise, you can take the plants to the landfill where they have to take it since these are weeds.

The downside to using broad spectrum herbicides is that they will most likely kill all the plants they hit.  Many times these invasive plants are growing amongst the trees, shrubs and herbs we would like to maintain, and so broadcast spraying of an herbicide could be counterproductive.  There are a number of ways to work around this issue.  One way to protect your good plants from the herbicide spray is by covering them with a plastic jug or sheets of plastic.  Some of these invasive plants (like buckthorn and honeysuckle) start producing leaves earlier in the year and hold their leaves later in the year than our native plants.  That makes it easier to find them and hit them with an herbicide without having to worry about affecting the plants you want to keep.

You can also use a combination of cutting and treating with an herbicide.  This works especially well for invasive shrubs, and is best employed in the fall.  Cut the stems leaving a flat surface and then spray that stem or stump with an herbicide.  The chemical is taken down into the roots readily and can kill the plant pretty effectively.

Finding and dealing with infestations when they are small and new is the best way of keeping your forest healthy and achieving your goals.  There is a lot of great information out there on how to identify many of the common invasive plants and ways of controlling them.  Check out some videos produced by the weed science folks of UW-Extension.

Tags: