Invasives Summer Wrap-up

Copyright ©2026 CT Invasive Plant Working Group (CIPWG)

Summer is the time for enjoying the outdoors and our yards. However, we do need to check for invasive thugs that may be lurking in our gardens, borders and woodlands. Extremely prolific and aggressive, they can destroy the plants and trees we care about, potentially spreading to our neighbor’s yards and beyond.

Oriental Bittersweet saplings can be found under trees where birds often perch after eating berries. These saplings are easy to pull before they send out “tentacles” that grab and climb onto shrubs and trees, eventually pulling them down. Larger vines can be cut and stumps immediately painted with an herbicide. We don’t recommend pulling vines out of trees since the tree can be damaged, but if branches with berries are within reach, they should be bagged to prevent spreading the seed to new areas. The same is true for Porcelainberry with lobed leaves and obvious bright blue berries.  Mile-a-Minute vine likes to blanket and smother shrubs and meadow plants. It can be pulled or weed-wacked but again, if berries are present, it is important bag the vines since seeds persist in soil for up to 6 years.

Invasive shrubs can be managed by cutting 6 inches above ground and stumps immediately painted with an herbicide. These include: Autumn Olive, Japanese Barberry, Multiflora Rose, Burning Bush, and Wineberry. If possible, bag anything with berries or pile in a designated area where resprouting/reseeding can be monitored, (not in compost or brush pile).  Invasives with berries can also be brought to the Newtown Transfer Station and deposited in the designated Invasive Plants Trailer, NEVER be placed in the brush pile.

Japanese Knotweed is trickier. Cutting stalks only encourages underground rhizomes (roots) to spread laterally and pop up in another area and should be avoided if possible. Herbicide treatment must be done within a specific window of time – after flowering to protect pollinators and ending two weeks prior to a killing frost. This is important because the herbicide needs to be drawn down to the roots to kill the plant. If treated too early, the herbicide only affects the leaves while roots remain viable. We recommend hiring a licensed professional, experienced in treating knotweed because the wrong concentration of herbicide will only burn leaves and not kill the plant. It’s not too early to contact a licensed professional for an appointment. For more information on Japanese Knotweed and to find a licensed applicator, go to: www.newtownknotweed.org

Tree of Heaven also requires targeting the roots with an herbicide between mid-July and mid-October when carbohydrates are flowing to its roots. Herbicides can be applied depending on the plant's size and diameter. Smaller plants use a foliar spray, stems less than 6 inches in diameter can utilize basal bark application, and diameters larger than 6 inches require hack-and-squirt. Another tricky invasive. Cutting and applying herbicide to the stump does not kill the plant, resulting in root suckering.

• For more information, visit the Penn State Extension site.

Each one of these invasives threatens our yards and wild places. Invasive vines smother and strangle valued trees and other plants. Invasive shrubs outcompete and displace native vegetation in woodlands to create unhealthy monocultures. Japanese Knotweed spreads rapidly to undermine and damage structures. Barberry harbors mice responsible for the spread of tick-borne disease. Tree of Heaven is a host plant for the destructive spotted lanternfly that, in turn, damages many of our valued trees. All destructive and dangerous, it’s an all-hands-on-deck effort to battle these dangerous invasives for protecting property and ourselves.
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The Newtown Conservation Commission is actively working to encourage healthy habitats and increase the diversity of our native wildlife and vegetation. www.newtownconservation.org