I see them from several yards away on the edge of the woods, and they dazzle. Picturesque and bucolic, clouds of white flowering shrubs cascade in a wild hedge along the tree line. As I get closer, my heart sinks; what I’d hoped were Delaware’s native Allegheny blackberry blossoms are instead the invasive multiflora rose.
The canes of the Allegheny blackberry have slight edges and are red or burgundy in color, but the multiflora rose has an olive-green, mostly smooth, round stem. It also has a fringed leaf-like attachment called a stipule—right where the leaf stem connects to the stalk of the plant, the shape looks a little like a centipede.
I learned to tell the difference between the two through my training as a master naturalist in a science-based program run jointly through the University of Delaware Cooperative Extension and the Delaware Nature Society. I spent a year deeply immersed in the wonders of the natural world, with hands-on experience identifying wildflowers, birds, insects, and amphibians—and, of course, studying native and nonnative species.
It was invasive plants that led me to the program. I had been keeping informal lists on index cards of what I saw blooming during my hikes throughout the year, and I quickly realized that I was finding not only native wildflowers but invasive plants as well—a lot of them.
“A non-native plant becomes invasive when it starts to spread uncontrollably, taking over and pushing out native plants.”
A ripple effect
The trouble with invasive plant species is that they compete with native plants, and that creates a harmful ripple effect throughout the ecosystem. They disrupt the native food chain and alter habitats by creating dense, shaded thickets. They also contribute to soil erosion, which ultimately affects water quality. These plants often produce fruit or flowers that are less nutritious than native plants, and when eaten by birds or animals, their seeds spread, continuing the cycle of invasion.
The Delaware Invasive Species Council website lists 100 invasive plant species in the state, with 16 more on a “watch list.” A plant that is considered native to Delaware is one that predates colonial settlement. Non-native plants arrived with European settlers, either escaping from their original purpose as protective packing inside crates or brought intentionally for things like decoration, food, or medicine. A non-native plant becomes invasive when it starts to spread uncontrollably, taking over and pushing out native plants.
One example of a non-native plant that turned invasive is the Callery/Bradford pear tree. According to Chris Bennett, environmental stewardship program manager for the Delaware Department of Natural Resources and Environmental Control (DNREC), “This woody invasive is one of the worst invaders of fields and meadows.” Originally propagated as a sterile version of the Callery pear, the Bradford pear became a popular tree with developers and landscapers because of its profusion of spring-blooming flowers. Further cultivars developed, and eventually the various pear trees cross-pollinated, resulting in “live” fruit, which was spread by birds and animals. The impact is easy to see in early spring, when masses of the white flowering trees bloom in dense patches along the roadside.
Bennett and his team continue to discover problematic plants throughout the state. “There are a couple other species that we are finding in our state parks that have the potential to become invasive,” he points out. Two are Elaeagnus multiflora (also known as cherry Elaeagnus and goumi), which they found and treated at Killens Pond State Park, and Elaeagnus pungens (silverthorn, thorny olive), which escaped from residential landscaping into the dunes of Delaware’s beach parks.
The invasive porcelain berry threatens native forests, especially in the Piedmont area of northern Delaware. Its leaves closely resemble those of a grape vine, and it blooms with a small pale-yellow-to-green flower in the spring. In autumn, those flowers turn into a variation of light blue, cream, teal, and vibrant purple berries—each with a speckled detail that makes them resemble tiny bird eggs.
With the potential to grow 10 to 25 feet in a single season, porcelain berry swiftly scrambles over native shrubs and trees, forming a thick mat of foliage that blocks out any sunlight. You have probably noticed it along our roadways, where entire stretches appear to be draped with a large leaf blanket, reducing them to one undulating stretch of green.
Cultivating solutions
It’s early spring, and the day has finally delivered some dry weather. A national historic park ranger hands out gloves, clippers, and protective eye gear to our group of volunteers, who have come to help remove invasive species in and around the remains of the old Ramsey barn in the Brandywine Valley unit of the First State National Historical Park.
We spend three exhaustive hours tugging, clipping, and clearing the previous season’s weeds and invasives, collecting them in massive heaps. It’s easy to settle into the work; the repetitive cutting and stacking creates a rhythm of movement that feels almost meditative. With our gloves covered in burrs, we stand back and look at what we accomplished—and any discomfort disappears.
There are plans on the horizon for the Brandywine Valley park site, and Joshua Boles, superintendent of the First State National Historical Park, is actively leading them. After heading up an extensive environmental assessment of the park, Boles is aware of the role invasive plants play in the degradation of natural lands and native species in the Brandywine Valley unit of the park. To tackle the problem, he foresees a continuation of the volunteer opportunities already in place, with the possible development of more structured teams to help target problem areas.
“[These teams would] remove clutter from the t.rails…t.rim back vegetation in the spring…and notify park rangers about more substantial issues,” he explains.
Since the Brandywine Valley unit alone comprises more than 1,359 acres of forested hills, pastures, and streams—and with only four permanent employees on-site, along with interns who come and go throughout the year—Boles welcomes the help volunteers provide.
Blake Moore, the natural resource agent at the University of Delaware Cooperative Extension, agrees that volunteers play a vital role in assisting park and state agencies with the removal of invasives. “The biggest challenge to invasive plant management is having enough resources, whether [it concerns] labor, funding, or awareness of the issue,” Moore says. “No agency controlling invasives has adequate staffing and funding to [fully] address invasive plants.”
Enacting change
Public awareness is growing, thanks to the efforts of the Cooperative Extension, the Delaware Invasive Species Council, and Delaware Nature Society, along with various other state and local agencies.
Senate Bill 22, sponsored by state Sen. Stephanie Hansen, with unanimous bipartisan support, was signed into law and went into effect on July 1, 2022. Known as the Invasive Plant Law, it bans the sale of 37 plants identified as invasive by Delaware’s secretary of the Department of Agriculture. These plants were commonly found at nurseries or used by professional landscapers. The law not only prohibits the sale of these invasives but also requires a label for plant species that might later be flagged as potentially invasive.
If, like me, you are eager to help, consider volunteering to remove non-native species. For a deeper understanding of the problem, the yearlong Master Naturalist program offers online lectures, a series of field trips and subsequent journal entries, and 40 hours of volunteer service. You’ll gain more than just a certification—you’ll meet a community of like-minded Samaritans who are just as interested and enthusiastic about making a positive impact.
Even as a graduate of the program, I don’t view myself as an expert. I see this certification as a foundation that I can continue to build upon through advanced training and ongoing volunteer work with the Winterthur Natural Lands Stewardship and state and national parks—as well as by connecting with other naturalists to exchange new insights.
The most valuable insight I’ve gained is a greater understanding of how deeply we are all bound together with the natural world and how much it needs our stewardship to continue to thrive.
For more information, visit destateparks.com and udel.edu.
