Ecology

The bad and the beautiful: spring invasives

Anne Gageby
Strawberry Hill Nature Preserve

(6/2024) During a sunny day recently, I went walking behind Strawberry Hill’s pond hoping to spot some turtles. I wasn’t disappointed. There were four resting on a long-fallen tree that dipped into the cool, dark water. As I continued up and around the Norway spruces that ring the pond and made my way toward the trailhead, I spotted something else – the beautiful bluish-purple flowers of lesser periwinkle blooming across the hillside.

Lesser periwinkle (Vinca minor) is a flowering plant native to Europe, western Asia, and northwestern Africa. It was introduced to the US in the 1700’s as an ornamental ground cover because of its ability to form dense colonies. It spreads by underground runners and does well in all light but thrives in heavy shade like we have at the start of the Orange Trail.

It’s an unfortunately lovely plant. I say unfortunately because it is quite stunning and adds a sprinkle of color against a sea of green. A real gem in a well-contained garden. But at best, at least as far as the forest is concerned, lesser periwinkle has little value to wildlife other than to pollinators, especially wild bees. At worst, it’s a quickly spreading invasive that chokes out more valuable natives and disrupts the natural forest succession process by forming thick carpets that prevent new growth from taking hold.

That’s the biggest problem with invasives. They disrupt the natural processes of an ecosystem and push out native species. They accomplish these tasks while giving little back. With few exceptions, they’re simultaneously beautiful and bad.

One invasive that leans heavily on the bad side is Japanese barberry (Berberis thunbergia). Its seeds feed some birds though most fall away untouched. There are far more desirable berries and seeds in a healthy forest, after all. It does provide a nice habitat for white-footed mice but also harbors everyone’s favorite parasitic arachnid: ticks. Barberry creates a microclimate within its structure that helps insulate and buffer extreme temperatures compared to native vegetation, an ideal living situation for tick populations. Its low stature and broad-reaching branches give ticks ample contact with animals and people. It’s prime real estate for ticks looking to reach more potential hosts but a problem for everyone else.

On the other hand, an invasive I watch out for is personally one of my favorite plants – English ivy. I am a sucker for a picturesque stone cottage with ivy-covered walls, or a wooden fence alive with sprawling ivy. And yet, I understand the whimsical notions I have of ivy and its gorgeous stretches of emerald vines belie a multitude of problems. Ivy (Hedera helix) can be quite dangerous to trees as its vines snake up and around trunks and branches. It "chokes" trees but not the way a boa constrictor chokes prey. Ivy forms dense foliage canopies that block sunlight and prevent photosynthesis.

Growing up, I often heard that ivy’s aerial roots dig into tree bark and kill trees by growing into the tree itself and robbing it of nutrients. It turns out this isn’t exactly true. Ivy does produce aerial roots, but they attach to trees for support, not parasitic absorption. It also damages tree bark by trapping moisture and creating an ideal environment for fungal rot to take over. Not to mention the added weight of those spreading vines which makes a tree more susceptible to falling during bad weather.

English ivy is an evergreen perennial in the ginseng family. It’s native to Europe, North Africa, and Western Asia. It, too, was brought here by settlers in the 1700’s to be used for cultivation. For years ivy has been heralded as a low-maintenance groundcover, a decidedly appropriate description. Once started, ivy takes no real effort to maintain and often requires radical efforts to get rid of. Ivy invades all sorts of spaces, both urban and rural and can do considerable damage to buildings and natural spaces. Despite this, I’m not sure I’ll ever stop loving the image of an ivy-covered cottage.

Another invasive that I secretly have a fondness for (and sizeable disagreement with) is multiflora rose. Multiflora rose (Rosa multiflora) is a perennial shrub native to East Asia, specifically Japan, China, and Korea, and was introduced over a hundred years ago as a rootstock for rose breeding programs. It was also widely planted in the early 20th century to help combat soil erosion and to create living fences for farm animals as it produces incredibly dense thickets. These thickets provide excellent cover for rabbits, bobwhite quail, and pheasants as well as provide food and nesting sites for birds. The leaves are eaten by deer, skunks, opossums, and more. And the rosehips are food for grouse, turkeys, bears, and chipmunks, especially during the winter when other foods are unavailable. This all sounds overwhelmingly positive, doesn’t it?

The problem with multiflora rose is its aggressiveness and ability to thrive anywhere. It’s not picky about sunlight, soil, or moisture, and it creates a seed bank that guarantees years of effort to fully eradicate. Unfortunately, the more you cut back multiflora rose bushes the more sunlight and space you give the fallen seeds to grow. The irony is when you fight it, you give it more opportunity to prove itself.

We’re fighting a losing battle in some areas of the state as these invasives and others take over. At Strawberry Hill, we’re constantly using mechanical efforts to combat invasives where we can but it’s not always effective or is only effective in the short-term. Long-term solutions such as planned eradication by use of herbicides aren’t an option as our mission includes maintaining healthy waterways and wildlife habitats. And prescribed burns are off the table. So, we manage as best we can with what we have.

Still, I sometimes walk amongst the multiflora rose, lesser periwinkle, and others and try to find some good in their existence, even in the smallest measurement. It isn’t always easy, especially with tick-harboring barberry. But it is nice to stop and smell the roses, so to speak. After all, the multiflora rose smells incredible.

Anne Gageby is the Environmental Education Manager of the Strawberry Hill Foundation. Strawberry Hill inspires stewardship of our natural world by
connecting the community with educational opportunities.
 Learn more by visiting StrawberryHill.org.