Invasive Plants of the Fall Landscape

Along with the autumnal colors of changing tree leaves, many shrubs and vines also add vivid hues to our landscape this time of year. Some of the most vibrant and recognizable colors of the understory can be attributed to invasive plants, such as fiery burning bush (Euonymusalatus), yellow leaved and red berried bittersweet (Celastrus orbiculatus), and the pink-, yellow-, or orange-colored leaves of Japanese barberry (Berberis thunbergii). 

Burning Bush

Asiatic Bittersweet

Now is a great time of year before plants lose their leaves to take stock of what is in your yard and, if you find that the bush you planted a few years ago before the sale of 33 terrestrial invasive plants were prohibited in Maine, to make a plan to remove invasive plants and replace them with native plants. Invasive plants have no natural checks and balances within our landscape and are successful at outcompeting native plants, which provide greater diversity, shelter, and food sources for native wildlife and pollinators. A list of native plants from the Wild Seed Project can be found heremany of which provide dazzling fall foliage while complementing the ecosystem they are part of. One need not look further than colorful viburnums ranging in size from shrub to small trees, the distinctive bark of the striped maple, or the aptly named Cinnamon Fern to add splashes of fall color that continue to be interesting and beneficial year-round. 

Cinnamon Fern

Maple Leaf

Unsure of whether you have an invasive plant in your yard or woods? The State of Maine’s Department of Agriculture, Conservation, and Forestry has great invasive online resources and Maine Natural Areas Program put together a handy Maine Invasive Plants Field Guide guide to carry with you. 

This fall when you’re planting, transplanting or making plans for next year, take the opportunity to pay attention to the soil in your garden beds and woods to look for clues surrounding your soil health and potential invasive pests that may be lurking beneath the surface. Documented by the state of Maine in Bowdoin, Brunswick, and Topsham since 2020-2021, invasive jumping worms are increasingly being found in yards, gardens, and forests. Jumping worms can dramatically change the soil, giving it a unique texture similar to coffee grounds, which is one way to identify areas where they are likely found a few inches beneath the soil surface. Our typical earthworms play an important role in soil ecology by burrowing and incorporating organic residues and amendments into the soil, enhancing decomposition and promoting nutrient cycling that benefits soil structural development. Jumping worms are found primarily in the topsoil and feast on mulch and strip vital nutrients from topsoil. This kills plants and increases erosion without returning nutrients to the soil, resulting in mortality of plants over time and greater difficulty growing plants, posing a threat both to gardens as well as forests. Recognizable when handled from their namesake “jumping”, these wiggling worms have a pink, smooth collar that also sets them apart from other worms in your soil. 

To learn more about invasive jumping worms, learn how to report them if you find them at your home, and read more about how to limit their spread, click here.

National Invasive Species Awareness Week

Exit holes (center) and egg laying sites (above and below exit hole) are signs of Asian longhorned beetle damage that are visible this time of year. Image: J. Formann Orth Massachusetts Department of Agricultural Resources

It’s Invasive Species Week!

The BTLT Stewardship team primarily manages the proliferation of invasive species during the summer field season by addressing problem areas of several plant species. These species include Asiatic bittersweet, multiflora rose, shrubby honeysuckle and Japanese barberry. However, winter can also be an excellent time to spot problem areas of other invasive species that may be lesser known!

Check out this article from the Maine Forest Service about some invasive species that could be more easily spotted this month as well as ways to help monitor forest health in our state.



Invasive Plants and Ecological Considerations on BTLT Properties

By George Jutras, BTLT Land Steward

“Invasive” species refer to a species that is not only not native to a particular area, but is actively displacing native species and changing the makeup of an ecosystem. While some invasives may garner headline-grabbing attention such as the European green crab marching along the Maine coastline, many other species of invasives, particularly plants, are slowly and quietly redefining the ecological niches they now inhabit.

The Maine Department of Agriculture, Conservation, and Forestry defines an invasive species if it carries these three characteristics:

  • Is not native to Maine;
  • Has spread (or has the potential to spread) into minimally managed plant communities (habitats);
  • Causes economic or environmental harm by developing self-sustaining populations that are dominant or disruptive to native species.

While invasive species can be found almost anywhere, plants fitting the MDACF definition are found most commonly and densely in areas at the margins of an ecological disturbance. Clear cuts, roadways, powerline corridors, housing developments, industrialized areas, and the margins of historic farmlands are all examples of lands that have experienced recent ecological disturbance. Like any plant species, invasives need an available ecological space, or niche, within an ecosystem in which to grow. It is after an ecological disturbance such as the clearing of land, when niches may be made available, that invasive species can often outcompete native species to recolonize an area.

A few Invasive Plant Species to Look Out For:

Norway Maple

Norway Maple Acer platanoides

The Norway maple is a native of northern Europe, but was introduced as a landscape tree in cities and suburban areas around the state as a fast-growing hardwood that provides a dense shade canopy. As a direct competitor with native Maine maple species (silver maple, red maple, and the beloved sugar maple), Norway Maple threatens these species in their own habitats by growing quickly and shading-out native saplings.

Asiatic Bittersweet Celastrus orbiculatus

Asiatic Bittersweet

Most iconic in late fall, Asiatic Bittersweet produces red berries with yellow covering that Mainers often make into festive holiday wreaths. Bittersweet was introduced as a landscape ornamental and historically spread by Maine DOT as fast-growing roadside cover for erosion control. Bittersweet seed is spread via bird droppings, but also through improper disposal of bittersweet wreaths (wreaths should be bagged and landfilled – or, preferably, not created or purchased at all). While Bittersweet climbs and eventually strangles trees, dense patches of the invasive species was also found in a 2011 study to harbor high tick populations.

Honeysuckle (Lonicera morrowi)

Honeysuckle varieties Lonicera morrowi, tatarica, japonica,  and maacki

The several varieties of invasive honeysuckle share similar traits. A Tall shrubby plant (6-10ft), honeysuckle can be distinguished by its paired leaves and when a stem is broken, its hollow pith. Several native varieties of honeysuckle exist, including the mountain honeysuckle which is endangered in Maine. Maine native species are much shorter (only 1-2ft tall) and all Maine native species have an exclusively solid pith making them easily distinguishable from their invasive counterparts. Invasive honeysuckle outcompetes natives in similar ecosystems due to faster growth and greater height. This plant can also establish dense stands that limit the movement of wildlife.

Japanese Barberry Berberis thunbergii

Japanese Barberry is a distinctive shrub with oval leaflets and thorns along stems that produces red berries in the fall. Turkey and Grouse love these berries which aids in its spread via seed, although plant limbs that touch the ground can produce roots, which increases the density of established colonies. Japanese Barberry was brought to the US as a replacement for common barberry which can host stem wheat rust, a fungus that has historically had a severe impact on wheat crops. Barberry has the greatest ecological impact when it can proliferate to grow in dense colonies to crowd out native understory plants, eventually altering mature forest ecosystems.

Autumn Olive

Autumn Olive Elaeagnus umbellata

Autumn Olive is a tall treelike shrub (10-20’) with long thin leaves with silvery undersides and no relation to true olive trees. Autumn Olive produces red fruits that are commonly eaten by birds and mammals but are poor in nutritional value. A study noted by the University of Maine Cooperative Extension found that Autumn Olive fruit contributes to malnutrition in migratory bird populations. Autumn Olive also creates ecological concern primarily with changes to forest understory as it eventually creates an unnatural midstory in open mixed deciduous forests.

Multiflora or Rambler Rose Rosa multiflora

Rambler Rose

Multiflora Rose is a bushy shrub with thorny branches most visibly identifiable when blooming in June, and difficult to distinguish from native raspberry and blackberry in other months. The rose species produces white flowers and is distinct from all native roses which produce pink flowers. Multiflora Rose proliferates rapidly and competes with native raspberry and blackberry species as well as other ground cover plants for the understory of forests and the margins of cleared land.


Additional Resources

Much of this article was written with the help of resources from the Maine Department of Agriculture, Conservation, and Forestry. Additional resources including a full list of invasive plant species in Maine and several helpful plant identification guides can be found at their webpage, here:

It’s National Invasive Species Awareness Week!

Wintercreeper, a Maine Invasive

If you google the plant “Euonymus fortunei,” or “wintercreeper,” you’ll get two different kinds of results. The first kind will detail a plant that has won the Royal Horticultural Society’s Award of Garden Merit, has cultivars named “Emerald Gaiety” and “Emerald Surprise,” and may be on sale at your local garden center for $39.99. The second kind details a plant that is listed on the Invasive Plant Atlas of the United States, was named an “alien plant invader” by the Plant Conservation Alliance, and often is accompanied by the words: “DO NOT PLANT.”

We sure got an “Emerald Surprise” when we realized this plant was growing rampantly at our Smart Property this summer. The Smart Property, one of our newest acquisitions, is a 3-acre floodplain forest on the banks of the Androscoggin River, filled with towering silver maples and green ashes and home to warblers and waterfowl alike. We first noticed the mysterious emerald evergreen vine climbing nearly to the tops of some of these trees, and saw that where it touches the forest floor, it transforms into a blanket of dense groundcover growth.  We can’t know for certain how or when wintercreeper first appeared at this property, but its proximity to the riverbank indicates that it hitched a ride on the Androscoggin River, likely after getting washed out of somebody’s garden upstream, and was deposited during a spring flood.

As stewards of our conserved lands, it is our responsibility to protect our properties from invasive species—which reduce biodiversity, threaten rare species, and choke out native trees and herbs. But there are many occasions and circumstances where the battle against invasive species feels futile—that you could spend your whole life cutting brush and yanking weeds, and you’d hardly put a dent in the waves of bittersweet, knotweed, honeysuckle, and barberry that seem fated to overtake our native landscape. 

However, this time is different: because this is only the second known wild population of wintercreeper in the state, treating this infestation means that we have a real chance to prevent this plant from creeping into the rest of the state and strangling floodplain forests from Salmon Falls to the St. John. And we weren’t about to let that chance pass us by!

So we spent a few days with our Regional Field Team yanking the vines down last week—they come off the tree with a satisfying zzzzzip!—and digging the roots out of the ground, but it will likely take a few years of active management to fully remove wintercreeper from the Smart floodplain forest. 


So if you’re looking for new plants to put in your garden, don’t just go with what’s on sale at your local garden store, because it may have ulterior motives for world domination. Please consider buying New England natives! The Native Plant Trust has published a database of great garden plants that also support our native biodiversity—learn more by visiting their website.