Invasive Plants Have R.I.’s Native Life in StrangleholdRepel
By FRANK CARINI/ecoRI News staff
Extensive stands of Japanese barberry, which can grow up to 6 feet tall, smother native plants and don’t support pollinators. (istock)
The intrusive plant was brought to the United States from Japan
and eastern Asia in the late 1800s. The ornamental is still used in residential
and commercial landscapes because of its fall coloring and deer resistance. But
the prickly shrub easily spreads into woodlands, pastures and meadows, where,
like many invasives imported from faraway lands, it chokes out native species.
Japanese barberry can
also be popular with ticks. A multiyear study conducted in Connecticut
looked at the relationship between the deciduous shrub, white-tailed deer,
white-footed mice, and deer ticks, also known as black-legged ticks. It found
that the larger amount of barberry in an area, the higher the prevalence of
deer ticks, which can carry Lyme disease.
The hearty species, which can grow up to 6 feet tall, has denser
foliage than most native species and, as a result, the invasive bush retains
higher humidity levels that ticks crave, according to the study published in
2010. The shrubs also provide nesting areas for white-footed mice, which are a
main source for larval ticks’ first blood meal.
Follow-up research in
2011 found that barberry-infested forests are about 12 times more likely to
harbor deer ticks than forests without barberry.
This past fall Pennsylvania became the
most recent state to include Japanese barberry on its list of invasive plants
that can’t be legally sold or cultivated. The sale of the multi-stemmed shrub
with needle-sharp spines has been banned in Massachusetts since 2009
and in New Hampshire since 2007. The sale of the
plant is also prohibited in Maine and Vermont.
Connecticut recognizes
it as an invasive, but nurseries there can grow and sell it. Connecticut does
prohibit the sale of other plants on its invasive species list, but barberry is
popular and the nursery industry lobbied against a ban. Big-box stores are still selling it,
even after the Connecticut Nursery & Landscape Association agreed to phase
out the most invasive barberry plants.
The sale of barberry is allowed in Rhode Island. In fact, the
Ocean State is the only New England state that doesn’t have a complete list of
noxious plants. While the other five states have a long list of invasive
species that are banned or at least identified in Connecticut’s case, the Rhode
Island Department of Environmental Management’s invasive plants webpage
notes the damage inflicted by non-native species but only mentions one:
phragmites, which aren’t sold at nurseries and garden centers.
“For more information and resources about invasive plant species in Rhode Island,” the state’s environmental agency directs those interested in the problem to a broken link on the website of the Rhode Island Natural History Survey, a small nonprofit that over the years, as DEM staffing and funding have been cut, has become increasingly relied on to help protect the local environment.
The organization’s executive director, David Gregg, said the
Natural History Survey and others have been working since the early 2000s to
get Rhode Island to at least create a list of invasive plants that should be
avoided, such as burning bush, privet and Japanese barberry.
Those efforts have continually stalled, thanks in part from
pushback from lobbyists representing nurseries, garden centers and growers who
have developed their businesses based on consumer demand.
This snarl of oriental bittersweet has climbed into
trees along a roadside in Portsmouth.
(Frank Carini/ecoRI News)
Shannon Brawley, executive director of the Rhode Island Nursery & Landscape Association (RINLA), said the organization favors a list but wants the industry to have a significant say in what species are listed or banned.
“We have to make sure we’re not collapsing someone’s business by
outlawing particular plants,” she said. “It takes a long time to grow them.
Nurseries are growing it and then they have to tear out acres and acres of
product, and it takes five to eight years to grow something else to sell. If
it’s not done carefully, there’s going to be an economic impact on these
businesses.”
Gregg said if that is the case then there needs to be a plan to
deal with the issue of economic hardship. But maintaining the status quo, he
added, can’t be an option.
Like many other non-native species, Japanese barberry can tolerate
a range of site and soil conditions, which means, like multiflora rose,
oriental bittersweet and autumn olive, it comes to dominate the landscape, and
can change soil chemistry.
Common barberry, a European invasive first brought to this country
during the 17th century, is shade tolerant, which allows it to easily invade
woodlands. It can reach a height of 13 feet.
Barberry, like other ornamentals brought in from overseas, spreads
from home and commercial gardens to open spaces and areas that have been
disturbed, such as roadsides. Barberry produces a lot of seeds and has a high
germination rate. Its seeds aren’t very nutritious for wildlife, but they are
eaten anyway and deposited in more areas, where more of the invasive becomes
established — part of a larger cycle that is crowding out native plants,
destroying habitat, and starving native insects and wildlife.
Tangles of bittersweet, forests of burning bush and heaps of
multiflora rose mar much of Rhode Island’s landscape.
“Invasive species are the second-greatest threat to biodiversity
after development when it comes to areas of habitat they wipe out,” Gregg said,
“It’s what wrecks the outdoor experience for people who want to relax in green
space. There’s a crack ton of it. It’s a physiological and cultural problem, as
well as an environmental and economic one.”
He noted both sides of the East Bay Bike Path from end to end are
full of invasives. “Good luck getting a view of the water. It’s like going
through a tunnel of phragmites.”
Brawley noted she gets out-of-state phone calls from people
looking to buy burning bush because of its intense red foliage. She provides
them with native alternatives that are similar but don’t suffocate woodlands
and coastal scrublands.
“I couldn’t in good conscience recommend the purchase of this
plant,” said Brawley.
She said most Rhode Island nurseries and garden centers don’t sell
burning bush, or if they do, it’s a sterile variety.
Burning bush was introduced to the United States in the mid-1800s as an ornamental plant for use in landscaping. The sale of it is prohibited in Massachusetts, New Hamphire and Maine, and the invasive is on watch lists in Connecticut and Vermont. (istock)
Douglas Tallamy, a University of Delaware entomologist and author of Bringing Nature Home: How You Can Sustain Wildlife with Native Plants and Nature’s Best Hope: A New Approach to Conservation That Starts in Your Yard, has been researching and writing for years about the threat invasives pose to native insects and wildlife habitat.
His work has shown that the transformation of native plant
communities into landscapes dominated by imported species and lawns imperil
insects, most notably caterpillars, and the birds and other animals that depend
on them for survival.
A paper he co-authored in 2020 reviewed the
research supporting the theory — which has had its detractors — that the
widespread displacement of native plant communities by non-native species is
contributing to insect decline. It found that our longtime fascination with
ornamentals over native plants is degrading the local environment.
Japanese knotweed can grow 3 inches a day and reach 10 feet in
height. Oriental bittersweet can climb to 60 feet, strangling host trees.
Tree-of-heaven can reach a height of 80 feet and grow to be 35-50 feet wide.
Glossy buckthorn can colonize without disturbance, and its dense foliage and
ability to mature quickly allows it to easily outcompete native plants.
Extensive stands of it can also produce conditions favored by deer ticks.
These four invasives and most others don’t have natural predators
feeding on or killing them. The vast majority of native insects can’t eat or
reproduce on these invaders — native plants and insects co-evolved over
thousands of years — creating a food desert for invertebrates and the birds and
animals that feed on them. They provide little support for pollinators.
Many of the worst invasives strangling Rhode Island, such as bittersweet,
knotweed and glossy buckthorn, are no longer sold, but the lack of diversity
created by the totality of the state’s invasive species problem, including the
continued sale of many intrusive plants, makes the local environment much less
resilient, by leaving it, for example, with fewer options when responding to
the climate crisis.
The continued sale of invasives is directly tied to consumer
demand and the Rhode Island landscape and nursery industry responding to those
wants.
Catherine Weaver, a RINLA board member and past president who owns
a North Kingstown-based landscape design studio, said her clients often request
miscanthus, also known as Chinese silvergrass, a popular ornamental grass she
called “a nuisance.” Hedges of invasive privet are also a high-demand request
by her clients. She called privet “a nasty invasive,” and said she instead
recommends the use of natives like sweet pepperbush or viburnums.
“We need to prioritize environmental integrity over aesthetics,”
Weaver said, “but we’re so used to using aesthetics to judge if a plant is
good. Planting something beautiful is pleasing … but we have to use other
criteria when we’re making these decisions. We shouldn’t be sacrificing
ecosystem function for beauty. We can have both. There are so many great native
plants.”
Both Weaver and Brawley said the public needs to be better
educated about the importance of native plants to create more demand. They
believe progress is being made on that front, albeit slowly.
“Five clients in the past year have asked for mostly native
plants,” Weaver said. “That almost never happened before.”
Not every non-native species is invasive, however. Invasives are
those that, reproducing outside their native range, actively cause ecological
or economic harm, according to the Invasives Species Act of 1996.
Species exchange is natural, as there has always been drift —
plants moving with the tides and seeds scattered by birds and storms. Ecosystems
change over time. Early humans brought hitchhikers with them as they migrated.
But comparatively, today’s invasive species levels are monstrous, because of
growing human globalization, including two-plus centuries of importation of
ornamentals from exotic places to show off wealth and later to keep up with the
Joneses.
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| A late-season crowd of sacred lotuses and clouds of algae impair Meshanticut Pond in Cranston. Despite previous attempts to cull lotus growth, they came back in full force last year. (Caitlin Faulds/ecoRI News) |
In Rhode Island, the limited amount of attention being paid to invasive plants is largely focused on aquatic invaders, which interfere with boating, paddling, fishing and other recreational activities. More than 100 lakes and 27 river segments in Rhode Island are plagued with at least one species of invasive plant, according to DEM.
The agency’s webpage for aquatic
invasives includes a list of the problem
species. Many only need a couple of cells or a leaf to reproduce. They can take
over a waterbody quickly.
In its 2020 fishing regulations, DEM prohibited the transport of
invasive plants on any type of boat, motor, trailer or fishing gear to help
prevent the inadvertent movement of aquatic invasives from one waterbody to
another.
DEM also has proposed regulations to
ban their sale, purchase, importation and distribution. The proposed
regulations list 48 species of aquatic invasive species whose sale would be
prohibited, such as Carolina fanwort, a problem species in Smithfield’s Stump
Pond; American lotus, which covers 18 acres of Chapman Pond in Westerly;
Brazilian waterweed, which has invaded Hundred Acre Pond in South Kingstown;
and common water hyacinth, an Amazonian species now found in the Pawcatuck
River.
DEM’s proposal to limit aquatic invasives is still under review,
according to an agency spokesperson. Enacting the proposal doesn’t require
enabling legislation.
Gregg said Rhode Island should be taking the same precautions when
it comes to terrestrial invasives, as they inflict as much damage to the
environment and local economy. He noted the fact Rhode Island hasn’t banned the
sale of many invasives or even bothered to compile a complete list doesn’t
paint the state as very neighborly.
He said it was also unfair that as taxpayers fund efforts to
eradicate invasives, nonprofits create programs to battle their spread and
volunteers spend their free time cutting and pulling them from the landscape,
their local garden center is selling more intrusive non-natives to be
unwittingly planted at homes and businesses.
“We’re spending good money and time removing invasives from the
woods to maintain the status quo,” Gregg said. “It would make more sense to
have a regulation that banned the sale of these plants.”
Gregg offered a solution: remove the word “aquatic” from DEM’s
invasive plant proposal.
“It’s pretty clean and simple,” he said. “Delete a single word and
create an invasives species list.”
A bill filed last year
would have done just that, making it illegal to import, transport, disperse,
distribute, introduce, sell or purchase in the state any invasive plant
species.
Black swallow-wort, an invasive vine from Europe, reproduces by sprouting new stems from existing roots and by spreading seeds. Inside this seed pod are thousands of seeds that will float on the wind or hitch rides on animals to other areas. Removing and disposing of seed pods before they open is one way of slowing the spread of this invader. (ecoRI News)
Two years earlier, in 2019, the Protection From Invasive Plant Species Act would have prohibited the planting of running bamboo within 100 feet of a property line. The fast-spreading invasive can penetrate asphalt and the siding of buildings. Many homeowners, not knowing the unintended consequence, plant running bamboo as a natural barrier that offers privacy and blocks out animals such as deer. But some bamboo species can grow 40 feet high and their roots can travel 15 feet in a year.
Violators would have been liable for the cost of removing the
plant from a neighbor’s property, plus any damages. Rhode Island retailers and
landscapers would have been required to provide customers written notice of the
risks of running bamboo.
To address other non-native invaders, the legislation would have
required DEM to create a list of invasive plant species, regulate their sale
and enforce compliance.
DEM, however, was opposed to the legislation. The state agency
said it already regulates invaders and can assess fines of up to $500 for
transporting invasive aquatic plants. It noted it doesn’t allow federally designated noxious weeds
to enter the state. The U.S. Department of Agriculture list doesn’t include
Japanese barberry, privet or burning bush. It doesn’t even include multiflora
rose, oriental bittersweet or phragmites.
The Rhode Island Farm Bureau feared the bill would punish farmers
for invasive species they didn’t actually plant. It suggested the state — that
is, taxpayers — instead offer money to farmers and property owners for the
removal of invasive plants, of which some were likely bought in Rhode Island
and planted by the current landowner.
Like past attempts to tackle the problem of invasive plants, such
as the 2021 bill that would have removed the word aquatic, the Protection From
Invasive Plant Species Act didn’t go anywhere.
Since the state seems unwilling to address the problem, Gregg said
the key to reducing the impact of invasives is educating the public about the
environmental harm many non-native plants cause.
“It’s in the public’s interest that we grow the right plants,” he
said. “The importance of native species has come a long way in the past 15
years, but we need an invasive species list so we can have conversations that
educate the public and bring awareness to the problem. It’s a complex issue,
but at the end of the day we’re spending money to remove stuff people are
buying at garden centers.”
