A Top Threat to Biodiversity: Invasive Plants

Non-native honeysuckle shrubs dominate this forest understory and have choked out native plants on Ricker Hill in Poland Spring, Maine. You can see this for yourself on Route 26, just across the road from The Lodge at the Poland Spring Resort. The dense green thicket below the trees are all invasive honeysuckle shrubs, native to Asia, which have aggressively out-competed the plants that should be growing in this forest.

“IT’S NOT THE FAULT OF THESE ORNAMENTAL PLANTS WE BROUGHT OVER FROM FARAWAY LANDS. IT’S ON US. WE JUST NEED TO DO WHAT’S RIGHT TO RESTORE THE NATIVE PLANT COMMUNITIES, AND WE NEED TO DO IT NOW BEFORE IT’S TOO LATE.”

I adore plants. It wasn’t always this way. In my early career, I was so distracted by the “charismatic megafauna” (black bears, and brown bears, wolves, and lynx) that I didn’t pay much attention to the plants beneath my feet. It’s funny what travel, time, and a lot of different experiences can do to your perspective. Don’t get me wrong, I will always be fascinated by large carnivores and those big, dramatic landscapes they roam. But over the decades I have discovered the almost hidden, often overlooked, and endlessly intriguing world of plants. The more I learn, the more questions I have. Above all, I have a profound reverence for the flora of our world.

Plants are the basis for terrestrial habitats that support our wildlife. To conserve wildlife, we must first conserve native plants. Non-native plants don’t serve a functional ecological role in our landscapes and have minimal wildlife value, in general. In fact, invasive non-native plants negatively impact wildlife habitat in a variety of ways, some of which we are just now beginning to understand.

Let me tell you a sad story about how our ecological naiveté gave rise to the spreading, creeping leviathans of the plant world that are now taking over some of our favorite woodlands and parks.

Take heart though, it’s not all doom and gloom.

I will also lay out some specific steps all of us can take to collectively stop the bleeding and restore native plant communities.

But first, the sad story with a cast of well-intentioned but ecologically short-sighted characters. In the 1950s and 60s conservationists, wildlife biologists, and state natural resource agencies encouraged farmers and other landowners to plant non-native fruiting shrubs for erosion control and wildlife habitat (because they were fast-growing and established quickly). These included Japanese barberry, multiflora rose, autumn olive, and buckthorn, among others. Let’s not forget the horticulturists and garden centers who enthusiastically promoted plants like burning bush (“gorgeous fall color!”) and “bamboo” (“fast-growing with a pleasing appearance!”).

Now we know that these plants routinely escape from cultivation and are invading our natural areas at an increasingly alarming rate. Now we know that these plants are invasive.

Please note: not all non-native plants are considered “invasive.”

By definition, an invasive species is a non-native species whose introduction does, or is likely to cause, economic or environmental harm to human, animal, or plant.

Invasive plants take over entire fields, forests, and roadsides.

Japanese knotweed, for example, is one of the most invasive plants in the world. It forms very dense, impenetrable thickets that shade out all other plants. It reproduces vegetatively by rhizomes (a continuous horizontal underground stem). It can easily spread to new sites via flowing water or in soil brought in as fill – even a small plant fragment can sprout into a new plant.

Knotweed grows at an incredibly fast rate and can reach up to 10 feet in a growing season. This aggressive plant prefers moist, open habitats and thrives along waterways, roads, and disturbed areas. Knotweed frequently colonizes riparian areas and is notoriously difficult to remove once established.

Japanese knotweed is one of the most invasive plants in the world and is notoriously difficult to remove once established.

It’s not the fault of these ornamental plants we brought over from faraway lands. It’s on us. We just need to do what’s right to restore the native plant communities, and we need to do it now before it’s too late.

Please understand this, I don’t want to demonize plants. I love plants. That is exactly why I’m so fired up about our collective need to aggressively remove and control the spread of these non-
native misplaced invaders, at the landscape scale.

When it comes to this topic, I am an ecological evangelist, and this is my core message:

In order to conserve biodiversity and wildlife habitat, we must take swift action to protect and release native plants from the aggressive competition and bullying behavior of non-native invasives – and there is no time to waste.

Let’s get started then, shall we?

How to Free Native Plants from the Grip of Invasives

Overall, a successful strategy to eradicate invasive species is a four-pronged approach:

1. Prevention
2. Early detection-rapid response
3. Control
4. Restoration

Here are a few things you can do to contribute to the overall success of native plant restoration in your community, beginning right out your own front (or back) door.

If these steps are too time-consuming or frustrating for you, or if you simply want to get started right away, and make sure to do it right, I can help.

I offer invasive plant assessments and can develop a customized removal, monitoring, and control plan for your property (of any size). Just connect with me here.

1. Identify & Detect

• Learn to identify invasive plants. There are several highly common ones that are easy to identify.
• The Maine Natural Areas program is a good source for photos and descriptions.
• Once you learn to identify them, share your knowledge with your neighbors, friends, and family.

2. Remove

• Use mechanical and hand-pulling methods wherever possible. This will be feasible in situations with low to medium density.
• For high density situations, consider a mechanical-chemical approach (work with me for more guidance on how and when to do this responsibly and safely).
• Although controversial, approved herbicides are an ecological tool when used responsibly, conservatively, and appropriately. Their careful, controlled use enables the restoration of native plant communities that support wildlife and overall biodiversity.
• Dispose of plant material properly (work with me for specific instructions for your site and species).

For larger stems that can’t be hand-pulled, use the Uprooter (a heavy-duty professional tool designed to pull woody plants). It provides great leverage for pulling the stubborn roots of Japanese barberry, for example (pictured here) and is a chemical-free technique.

3. Prevent

Prevent further spread and infestation by monitoring your property often, at least twice a year – ideally, in the spring and fall.

Overall, regular monitoring for invasive plants and early detection is critical.
Once detected, rapid response (treatment and removal) is imperative to prevent their spread. Early spring and late fall are excellent times to look for invasive plants because they are the first plants to leaf out in the spring, and the last ones to lose their leaves in the fall – making them much easier to spot (as you can see from the photo of the honeysuckle under our first fall snow, at the top).

Mark the locations of individual plants and infestations with a GPS or on a map so you may return to the site after treatment to check for re-sprouting.

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Did you know? Japanese knotweed is edible and has many health benefits and medicinal uses, including as a treatment for Lyme disease. If you can’t beat it, EAT it!?

by Deborah Perkins, M.S. – Wildlife Ecologist
Originally published on November 14, 2017