Posted: July 25, 2017

As long as light and other resources are available to invasive plants, they will continue to out-compete native plants and spread. What can landowners do to control these invaders?

A common refrain heard from woodland owners by our team at the Center for Private Forests at Penn State, along with other extension educators, is, "I don't know where to start!" It's a sentiment especially common to people who are new to owning and/or new to taking an active role in forest stewardship. Almost always, our first response is to inquire, "Do you have invasive plants on the property?" Realistically, if there are invasive plants present in and around the woodland, getting them under control is a first priority.

You may already have some ideas and objectives for your land like doing some thinning to improve a stand of trees or planning a harvest to encourage the growth of new trees. As any service forester or consulting forester will tell you, to be successful at these objectives, any invasive plants must be controlled, so they don't take over the growing space and resources made available by the removal of trees. Likewise, even if you don't have any tree thinning or cutting in your plans, as long as light and other resources are available to invasive plants, they will continue to out-compete native plants and spread.

"Invasive plants" are so-named because they invade and gradually overtake areas occupied by native plants. Frequently, they are fast growers, have longer growing seasons, and grow in areas far from the animals and other plants that would limit their growth in their natural range. Their abundance in an area actually degrades that habitat, as native plants and animals are displaced. Invasive plant species do not provide the same food value to wildlife as native plants do. Without active efforts to control their spread, invasive grasses, forbs, shrubs, and trees can have lasting effects on forest composition and vitality.

Fortunately, the level of awareness among woodland owners, (as well as the public in general) seems to be improving. Landowners frequently ask about the best control methods for different species, and there are a number of helpful resources on the internet for identification and control. Several particularly helpful sites are Invasive.org, Invasiveplantatlas.org, and EDDmaps.org (all three sites are hosted by the Center for Invasive Species and Ecosystem Health at University of Georgia and multiple partners). The EDDMaps site not only has identification and control methods, but also gives an opportunity for citizen scientists to help with mapping invasive plants' distribution.

Even when equipped with information about how to control each invasive plant species, one can easily feel overwhelmed with the task of getting started with the control methods. "Which area should I start with first?" Perhaps counterintuitively, invasive plant experts recommend prioritizing the smallest populations of invasive plants for management. The rationale: first, prevent spread and maintain areas of low impact from invasive plants; second, rescue native plant communities that are currently in battle with invasive plants; and third, take on the toughest job, to restore an area dominated by invasives to a more diverse and native woodland plant community.

For example, if you have just a few bush honeysuckle shrubs, it is physically easier, cost-, and ecologically efficient to kill these few shrubs now. Prompt action allows the area to be maintained as invasive free by preventing the further spread of bush honeysuckle on the site. This maintenance is a priority since it is critical to prevent the establishment of new populations of invasive plants that would be highly competitive with native woodland shrubs and herbs.

Some areas in and around your woodland may have larger groupings of invasive plants, but with a number of native plants still surviving. These areas should be second on the list in prioritizing your control efforts. Reducing the invasive species in areas where native plants have not yet been displaced will allow the native plant communities to recover from the stress of having to compete. Because the invasive plants are more established in these areas, the efforts to control them will require your attention for at least a year beyond the initial effort--primarily, monitoring for new growth and resprouting, and follow-up control. The effort required is greater, but to see the return of native plants and their ecological function is a likely and significant reward.

Last on the list of areas to prioritize invasive plant control efforts are the areas that are already completely occupied with invasives. Examples include monocultures--large groupings of a single plant species, and in this case an invasive species--or areas with dense growth of several invasive species such that no native plants are left alive. These areas are so dominated by invasive plant species that they may need to be replanted after the invasive plants are under control. Of the prioritized areas, this type of invader requires more effort and will take the longest, because the need has gone from "rescue" to "restoration."

In the midst of summer heat, it's sometimes hard to think of getting out there to do the labor involved in getting invasive plants under control. Don't worry, though--even taking the steps to gather information and develop a plan are very important. Here are some steps you can take to help minimize feeling overwhelmed and get you ready to take action:

  • Print an aerial map of your property from Google Maps, GoogleEarth, or other map sites. You can then make notes and label areas in which to work.
  • When you're in your woods, carry some brightly colored flagging to mark individual invasive plants or small populations as you encounter them. The color of the flagging might provide a visual reminder that areas with few invasives are priority areas that need to be addressed first. Use a different color for each priority level described here.
  • Reach out to your local PA DCNR Service Forester to have a walk and talk in your woods. He or she can help brainstorm a timeline of activities, and point you to more resources for learning.
  • Research the species that you're dealing with, noting the season that is most recommended for treatment.
  • Research some optional tools for your toolbox: You can find reviews of actual tools for you to do the work yourself at: https://www.invasive.org/gist/tools.html, https://www.invasive.org/gist/products/library/herbsafe.pdf, and http://extension.psu.edu/publications/uh174, for example.

When you've determined the priority level for taking action on groups of invasive plants around your property, and after you've assessed the best timing for controlling the species you have, you can have greater confidence that your actions will be effective. The challenge of taking action is something in which you can involve others. You may have family gatherings into which to incorporate a work party. Break the work down into tasks that can be delegated according to age and/or skill-appropriateness-- help with piling brush after it's cut, for example. If you want to hire someone to complete the work for you, a good starting point is to search for Technical Service Providers registered on the Natural Resources Conservation Services website, or asking for the list at your county NRCS office (usually housed with Farm Service Agency). When neighbors see each other working on projects, it's natural to have some curiosity. Take advantage of that curiosity--share what you're doing and why. Chances are that your neighbor has the same invasive plants, and you may be able to help each other with the control activities.

James C. Finley Center for Private Forests

Address

416 Forest Resources Building
University Park, PA 16802

James C. Finley Center for Private Forests

Address

416 Forest Resources Building
University Park, PA 16802