The Invaders Among Us!

By Beth Sullivan

This has been a spectacular year for plants. The wet spring encouraged lush, vigorous growth. It would seem that all things are rejoicing at the end of the drought and adding life giving extra foliage to every branch and stem. We are also learning that most plants benefit from the rising levels of carbon dioxide in our atmosphere, which also encourages plants to photosynthesize more, adding more growth. I guess that is a good way to try and balance the CO2. However, we are also being told that vines, in particular, seem to respond most robustly to these growing conditions. Sadly, it appears that the non-natives are more efficient even still. It seems that right in front of our eyes, no time lapse needed, invasive vines are beginning to dominate: the woods, the trails, structures, native plants, and even each other. One native also enjoying the growth spurt is Poison Ivy, which seems to be the happiest of growers. It seems to be thriving better, growing larger and also seems to be more irritating.

Poison Ivy is a native that is behaving aggressively under ideal growing conditions.

Take a walk on one of several of our most beloved preserves, the ones with variable habitats, with fields, and open sunny patches along the trails and beautiful stone walls. These offer the most extensive look at how the invasives have altered the landscape. The Knox Preserve is a best (or worst) case example.

Walking down the trails along the field, and into the shrub land area, and along the shore, the variety of invasives is educational and daunting. Vines can be woody and persistent, growing bigger each year, such as Oriental Bittersweet which can entangle and strangle, and the monster Porcelain Berry that covers and smothers entire trees.

Oriental Bittersweet vines twist their way up and then strangle the supporting tree.

Porcelain Berry is a beauty of a beast that will cover and smother entire trees and walls.

Another invasive vine that has become a true problem for us is Black Swallowwort. The vines are delicate in appearance; they do not survive the winter. But underground their roots form a very dense, impenetrable mass. They are impossible to pull out successfully, and once established they form huge colonies, and other plants cannot get a foothold into the ground where the roots take over everything. The pods, which are visible now, look like slim, hanging milkweed pods. It is the similarity to milkweed that makes this plant especially loathsome. Monarch butterflies are somehow attracted to this plant and will deposit their eggs on the leaves. However their caterpillars cannot survive on them. Monarchs are having enough trouble in their life-cycles; they don’t need an added villain decimating their numbers.

If you find Swallowwort, at least remove the pods to prevent seeding

Other invasives are woody shrubs, like Multiflora Rose, Winged Euonymus (Burning bush), Japanese Barberry and Honeysuckle, or small trees like Glossy Buckthorn and Autumn Olive. Each of these plants might seem to offer some positives for wildlife: Multiflora Rose provides nesting places and habitat. Honeysuckle and Buckthorn offer appealing berries. Once again, there are hidden dangers. Birds rely on native berries for their nutrients for all aspects of growth and development. In a recent study, it was found that birds who took a greater proportion of their diet from non-native berries may get filled up, but the nutrients are not adequate to fill their essential needs-like “fast food” for birds. Birds that ate too many Honeysuckle berries had poorer feather development, poorer colors, and those colors act as attractants to females, as indicators of good health and vigor.

These are just a few. There is Japanese Knot weed, Spotted Knapweed, Mugwort and large Thistles. There are invasive grasses like Japanese Stilt Grass and Reed Canary Grass that take over and ruin grassland habitats. And there are flowers that have been planted in our gardens, like Lesser Celandine and Garlic Mustard, that have now run rampant, excluding other plants with the strength of their growth and even harmful chemistry. The list is, sadly, way too long.

Check out the CT Invasive Plant Working Group web site here.  The working group is a consortium of individuals, organizations, and agencies concerned with invasive plant issues. The website is quite an education. Their plant list is here.

Take some time to look around your yard and woodlot. This is the time now to identify them most easily. Then pull, cut, treat and remove as many as you can before they spread. Don’t let those berries be eaten; don’t let the seeds blow. Dispose of plants in your trash, and do not put into yard waste containers that will be sent to compost.

We have introduced these plants to our native habitats. They threaten native plants and are detrimental to native pollinators, birds, and other animals. I believe it is our responsibility to try and control them the best we can.

 Photographs by Beth Sullivan.