Field Notes

5 plants to watch for this fall (and why we aren’t calling them invasives)

5 min read / October 11, 2024

Their foliage is often seen as beautiful... but they can forever alter the landscape.

Haven’t seen as many monarchs this year? Did you watch a beloved maple tree die off?

It could be because of a plant commonly referred to as an invasive species. (There’s a recent shift to calling them introduced species instead; more on that below). There are many plants that are quietly reshaping Vermont’s landscapes and biodiversity. Many are easier to identify in the fall because of their foliage. You may have even purchased one of these plants at your local garden center because it looks pretty.

Let’s explore why we’re changing our language around what was once known as invasive species, why they matter, what to look for, and what you can do.

Why we’re calling them introduced vs. invasive species

Humans tend to put species (plant or animal) into two buckets: native and invasive. Native equals good, and invasive equals bad. Yet, it’s not that simple.

Just because a species is introduced to an area doesn’t mean it’s highly competitive and causes significant ecological, economic, or health damage. Many are harmless. Yet, terms like “invasive” and “aggressive” are negative and lead to a mindset that demonizes species.

These words can also have unintended consequences, such as xenophobia, when plants are associated with the countries where they originated. Shifting the language puts the goal on protecting native ecosystems rather than framing it as a fight against what’s foreign.

Some organizations are shifting from the term “invasive” to “introduced” species to foster more thoughtful, respectful language. We are exploring making this shift at VLT in collaboration with partners like the Vermont Agency of Agriculture.

Changing our language takes time, and while “introduced species” doesn’t exactly roll off the tongue yet, we’re giving it a go. Please let us know if you have thoughts or an experience to share.

Why do native species matter?

Native species support diverse wildlife and our state’s biodiversity. As author Doug Tallamy has written, oak trees support more life forms than any other North American tree genus. These trees in turn, support insects, amphibians, reptiles, birds, and mammals up the food chain. Native plants also support higher numbers and varieties of fungi, maintaining healthier soils.

Introduced, highly competitive species can make it hard for native species to survive. They often don’t have natural predators because they didn’t evolve here, like the Emerald Ash Borer.

These species make our landscapes less friendly for other species, offering less ground cover and less nutritious, or even toxic, food. For example, Monarch butterflies sometimes lay eggs on swallowwort, which is in the same family as milkweed but is poisonous.

Below are five introduced, highly competitive species that are easier to see in the fall in Vermont.

1. Barberry

How to identify: Look for narrow red berries hanging down along the underside of branches. The plant has sharp, thin spines at each leaf node. If you pull up the roots, they’re a striking yellow. Leaves are small and spatula-shaped; the plant often takes on a reddish hue in the fall.

Why they are a challenge: Barberry can dominate the forest understory, preventing native species from regenerating. Its dense stands are also associated with higher populations of rodents and ticks, increasing the risk of Lyme disease. Birds love to eat the berries, which are like junk food, spreading the seeds and worsening the problem.

2. Burning Bush

How to identify: This plant has unique “wings” on its twigs, which are green in the growing season. Its brilliant pink and red fall foliage makes it a favorite among landscapers and homeowners and helps it stand out in the forest.

Why they are a challenge: Burning bush is a heavy seeder and can quickly dominate an area, outcompeting native species for light and nutrients. Its widespread planting as an ornamental shrub has led to its escape into wild areas, where it disrupts natural ecosystems.

3. Bittersweet

How to identify: Vermont has only three to four kinds of vines. This vine has light brown bark with raised bumps and tends to spiral around trees, strangling them. In comparison, a native grapevine is dark brown and flaky. In the fall, introduced bittersweet has bright, orange-cased berries that crack and turn red, while native bittersweet berries have more of a yellowish-orange casing.

Why they are a challenge: Introduced bittersweet vines kill trees by girdling them and weighing down their canopies. People often use them in fall decorations like wreaths, and when these are discarded in nature or compost, the seeds spread and create new infestations.

4. Glossy/Common Buckthorn

How to identify: Buckthorn’s leaves have veins that curve toward the leaf’s tip. Common buckthorn’s leaves are serrated, while glossy buckthorn’s are smooth-edged and shiny. Both types have alternate branching. The roots of glossy buckthorn are red with golden, fine feeder rootlets. The inner bark of common buckthorn is bright orange.

Why they are a challenge: Buckthorn is highly adaptable, thriving in a wide range of soil types and ecosystems. Once established, it outcompetes native species and prevents forest regeneration.

5. Honeysuckle (excluding natives)

How to identify: One way to tell introduced honeysuckles apart from native species is to clip a branch. If the pith (the center of the branch) is brown and hollow, it’s an introduced species. If the pith is white and solid, it’s likely native.

Cut stem of introduced honeysuckle that shows hollow pith.

Why they are a challenge: Honeysuckle creates dense thickets in the forest understory, making it difficult for native plants to grow. Like barberry, it is associated with higher tick populations, posing additional risks to wildlife and humans.

What you can do

Don’t spread them! Be cautious about using these plants in decorations (such as bittersweet wreaths) as this can unintentionally introduce them to new areas.
Learn to identify these species. Fall is the perfect time to spot many of these introduced plants, as their distinctive foliage stands out.
Take action early. Early treatment and removal of these species can improve biodiversity in your backyard or community.

By identifying and managing introduced species, we can help protect Vermont’s native ecosystems and the wildlife that depends on them.

Assistance is available

Check out VT Invasives for treatment options and the National Resources Conservation Service (NRCS) in Vermont for grant programs that may help with hiring contractors for larger removal efforts.

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