A frequently heard question in discussions about invasive plants is “How do we get rid of them?” The answer is simple, but not easy: cut, dig, pull, repeat. Monitor the area for re-growth, then cut, dig, pull and repeat! Plants from away become invasive because they are very good at surviving. According to the Maine Natural Areas Program website, a plant is defined as invasive if that plant is “not native to a particular ecosystem, and its introduction does or is likely to cause economic or environmental harm or harm to human health. Invasive plant species often lack natural predators, diseases, and other pathogens that keep them in check in their native habitats. They have competitive adaptations including early leaf-out, aggressive reproductive strategies, and efficient dispersal methods.”
Many plants labelled invasive will produce new growth when cut back. If pulled or dug out, the root fragments of some plants will send out new shoots. Plant parts will take root where they are discarded. Japanese barberry cuttings will take root if left on moist ground. Japanese knotweed will grow anywhere it is tossed when pulled or cut. These invasive plants are very good at surviving! They are difficult to eradicate. This is why they are called invasive.
So, what does one do to help control the growth of the invasive plants? Cut, dig, pull, and repeat. Spring rains moisten the soils to ease the removal of newly-sprouting bittersweet, multiflora rose and others. Japanese knotweed eventually disappears after repeated cuttings throughout the growing season. Just be sure to bag all those cut parts and dispose of them in the trash, then return to the site next spring and start again!
Tactics and Tools
One useful weapon in the battle with invasive plants is a weed torch. I use my weed torch on the small weeds growing between the bricks in my walkway. I also tackle Japanese barberry in the woods with the torch. Use loppers to hack the barberry down to stubs at the root crown, then torch those cut ends, charring them while avoiding leaf litter or other flammable materials. There may be some re-growth the following year, so you will need to re-cut and torch the stumps again.
A black plastic bag with twine is another weapon for the battle. Shrub honeysuckle can be very difficult to eradicate. Cut the shrub down to the root crown, then cover the stumps with heavy black plastic (a contractor’s trash bag is perfect for this!). Tie the plastic securely around the stumps, and wait a year or two. This method was tested on the shores of Harpswell Sound, where other methods could not be used, and after two years under cover, the honeysuckle shrubs showed no signs of life.
Finally, if nothing else can be done, cut the flowers to prevent the plant from producing seeds. When doing this, I bag the flowers to avoid the chance that seeds have begun to form, then dispose of the bags in the trash. Remove the rose hips from the multiflora roses. Bag the seed pods of black swallow-wort and the berries of asiatic bittersweet. You may not be ridding the area of the invasive plants that are already present, but you are preventing the next generations from taking root. And then, next year, go back and do it all again! Be assured though: over time you will often see improvement from your efforts and ongoing perseverance.
For more information on specific invasive plants found around Harpswell, please see the HIPP Invasive Plant Guide.