Invasive plants can significantly alter our forested landscapes, negatively impacting plants, animals, their habitats, and the natural processes of which they are a part.

Left unchecked, they can take over and dominate entire areas. Worse, invasive plants can alter soil chemistry and local ecosystems -- setting the stage for other invasive species to follow.

Invasive Species Bring More Invasive Species

Tree-of-heaven is an extremely aggressive invasive tree. It doesn’t take long for landscapes to transition from one or two stems to thousands.

Tree-of-heaven releases chemicals into the soil that inhibit the growth of native plants, which tends to encourage other exotic species that evolved with it overseas.

For this reason, areas overgrown with tree-of-heaven frequently also have infestations of barberry, Japanese stiltgrass, multiflora rose, and Asiatic bittersweet.

As native acreage is lost, native animals that feed on plants concentrate their feeding into smaller areas of leftover native plant communities, inflicting unbalanced harm.

Sustained overgrazing often kills native plants, opening more sites for invasive species to populate, accelerating the ecological damage.

Invasive Species on Michaux State Forest

Invasive plants are a major problem in Michaux State Forest [Adams, Cumberland, Franklin counties]. Common invasive plants there include: Mile-a-minute, Tree-of-heaven, Japanese angelica tree, Japanese barberry, Autumn olive, Japanese privet, Japanese stiltgrass, Multiflora rose, Japanese knotweed, and Poison hemlock.

Many of these invaders arrived by illegal dumping of yard waste, which often contains seeds and viable roots and shoots of invasive species.

Aggressive Response

Infestations of invasive species are taken very seriously. DCNR’s Bureau of Forestry uses an “early detection rapid response” protocol whenever a new invasive is found, which usually destroys the invasive species before it becomes a problem.

Due to the sheer number of acres the bureau manages, it is impossible to notice all outbreaks -- leading to unintended infestations.

Such was the case for a 400-acre Japanese barberry infestation near Pine Grove Furnace State Park [York County].

The Bureau of Forestry utilized an herbicide treatment program for several years in the area, essentially eradicating the unwanted invasive.

Follow-up spot treatments are routine, and the area will eventually be replanted with native species.

Get Help If Necessary

The invasive plant problem can be daunting, even for our hard-working foresters.

Sometimes it is necessary to call in reinforcements – like, in 2016, when Michaux staff used contractors to eliminate a 95-acre stand of cork and bee-bee trees near Mont Alto.

Staff continue to work on a management plan to treat an additional 202 acres in this region.

The Bureau of Forestry also uses “biological controls,” releasing plant-eating weevils to control the mile-a-minute weed.

These insects have been shown to target the invasive weeds, while avoiding native plants.

Although the weevil will not eradicate mile-a-minute weed, it does have the ability to control its spread.

Keeping Up the Fight

Part of DCNR’s mission is to conserve native wild plants. In order to achieve this goal, control of invasive species is crucial, and we hope Pennsylvania citizens will help us in this fight.

Things You Can Do

-- Plant only native plants at home and encourage others to do the same

-- Eliminate invasive species in your landscape

-- Never transfer yard waste to new locations

-- Participate with local conservation groups to do invasive species “roundups”

Learn more about invasive plants in Pennsylvania and how you can help control their spread at DCNR’s website.

[Visit the Department of Agriculture’s Noxious, Invasive And Poisonous Plant Program webpage for more on Pennsylvania’s Noxious Weed Control Law and Noxious Weed Control List.

[Learning to identify invasive plants is the first step in understanding and combating the problem. If you see one of these species -- report them at the Pennsylvania iMapInvasives website.

[For more information on state parks and forests and recreation in Pennsylvania, visit DCNR’s website, Click Here to sign up for the Resource newsletter, Visit the Good Natured DCNR Blog,  Click Here for upcoming events, Click Here to hook up with DCNR on other social media-- Facebook, Twitter, YouTube and Flickr.]

(Photo: Volunteers help remove invasive Japanese knotweed.)

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[Posted: February 29, 2020]

3/2/2020