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A Top Threat to Biodiversity: Invasive Plants

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Updated November 8, 2023

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 d…

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 altogether out-competed the plants that should be growing in this forest.

“It’s not the fault of these plants we brought over from faraway lands. It’s on us. We just need to do what’s right to repair and restore native plant communities.”

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. 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.

Non-native plants do not share an evolutionary history with our native insect communities, and therefore do not support insect populations which are the basis for diverse, and healthy wildlife communities. Non-native invasive plants threaten biodiversity and degrade the quality of wildlife habitat by compromising the integrity of natural plant communities.

Let me tell you a sad story about how our ecological naivete gave rise to the invasive plants 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 protect 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 can form dense monocultures in our increasingly precious wild and natural areas. Now we know that these plants are invasive.

Please note: not all non-native plants are "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 can 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 plant can quickly move into moist, open habitats and thrives along waterways, roads, and disturbed areas. In an alarmingly short amount of time dense stands of knotweed effectively modify and disrupt riparian ecosystems. The plant is notoriously difficult to remove once established, and the plant is even bringing down real estate values - considerably, in some places.

Japanese knotweed is one of the most invasive plants in the world 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 plants we brought over from faraway lands. It’s on us. We just need to do what’s right to repair and restore native plant communities.

Please understand this, I don't want to demonize plants. Plants are our allies, our medicine, and our food. Nearly every creature on Earth owes it existence to plants. This is exactly why I'm so fired up about our collective need to proactively control the spread of invasive plants - at the landscape scale. As we remove and control invasive plants, we release native plants so they can flourish into the future, thereby building better habitats for all life.

Perhaps even more importantly, we need to take our work one step further and meaningfully restore disrupted ecosystems. Restorative landscape practices can literally heal the landscape by creating conditions for biodiverse and resilient native plant communities that will thrive in the face of climate change and other environmental stressors.

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 - and there is no time to waste.

Let's get started.

How to Release Native Plants + Promote Biodiversity:

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

1) prevention, 2) early detection-rapid response, 3) control, and 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 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 as part of a landscape consultation and can develop a customized removal, monitoring, and control plan for your property (of any size).

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. I also recommend using the Maine Invasive Plants Field Guide.

  • Once you learn to identify these plants, 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. Minimize soil disturbance as much as possible.

  • 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 (download this species-specific resource from the University of New Hampshire FMI).

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 chemica…

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) Monitor & 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.

 4) Restore

  • Invasive plant removal and control will allow for native plant restoration which will significantly enhance wildlife habitat by repairing the food web. Over the long term, biodiversity will increase, which will create a more resilient landscape in the face of climate change and other stressors.

  • In some cases (especially when the invasive density was/is low) native plants will “volunteer” after being released from the competition for light, space, water, and nutrients.

  • In situations where the density of invasives was/is high, a persistent seed bank or root system may result in the continual sprouting of new plants. Soil disturbance from removal activities will exacerbate this. In these cases, dense plantings of native plants is required to restore the area.

  • There are many vigorous, fast-growing native plants that are well-suited to this task. For every piece of ground there is a native plant suited to grow on it.

  • Proper site prep, planting methods, and care are critical to ensure success.

  • Consider working with me to get custom recommendations on restoration plantings for these areas.

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!?

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#ThePersonalEcologistI partner with eco-minded landowners to create thriving wildlife habitats in their backyards, gardens, fields and farms, woods or campuses - at any scale.I have 25 years of experience in my field, and a lifelong commitment to wi…

#ThePersonalEcologist

I co-create biodiverse habitats with eco-minded stewards throughout the Northeast - at any scale.

I have 30 years of experience and a lifelong commitment to wildlife conservation.

Read My Story.

Deborah Perkins