Fall is an excellent time to assess the landscape for those sometimes attractive invasive species that surreptitiously get into our gardens. When most other plants are fading, drooping, and basically dying, these hardy plants become quite visible.
(Editor's Note: This article was originally published on October 26, 2011. Your comments are welcome, but please be aware that authors of previously published articles may not be able to respond to your questions.)
Though there are hundreds of invasive species throughout the country, the focus of this article will cover three vining plants of special concern to the home owner and small acreage farmer: Mile-a-Minute Vine, Oriental bittersweet, and Bittersweet nightshade. These hardy perennials don’t grow in all parts of the country and are only considered invasive in some states, obviously those where the plant thrives on the growing conditions.
Mile-a Minute Vine The recent hew and cry about Mile-a-Minute vine (Persicaria perfoliata) is not unfounded. This native of the Far East is a serious threat to our ecology, as it generally colonizes quickly in open and disturbed areas, or basically anywhere it can gain a foothold. It can grow almost 6 inches per day, outcompeting native vegetation by smothering everything and preventing photosynthesis. A member of the buckwheat family (Polygonaceae), it has also come to be known as the “Kudzu of the North”. As of 2011, it has been found in Connecticut, Delaware, Massachusetts, Maryland, New Jersey, New York, Ohio, Pennsylvania, Rhode Island, Virginia, West Virginia, and Washington DC. However, it has the potential to spread to most parts of the United States.
The plant is quite distinctive with bright green alternate triangle-shaped leaves and curved barbs along the stems and on the underside of the leaves. The white ﬂowers are small and inconspicuous, producing glossy, hard black or red-black seeds from June through October in the more southern regions; these seeds can remain viable in the soil for as long as six years (Plant Conservation Alliance’s Alien Plant Working Group).
Many states, including Connecticut, have watchdog sites where sightings of this plant may be reported. The key to keeping invasive plants from spreading is careful monitoring and control. Several options for management of this weed are available on the PCA website.
Oriental bittersweet (Celastrus orbiculatus) is native to eastern Asia, Korea, China, and Japan and, today, is an unwelcome visitor in North America. Used extensively in the late 1800s as an ornamental, it made itself quite at home. On close comparison, it is easy to distinguish this vine from the ornamental American bittersweet (Celastrus scandens), but American bittersweet has declined or become hybridized and is not so common, leaving its Asian cousin to take over.
Once Oriental bittersweet takes hold in a landscape, it is almost impossible to get rid of it, especially on large properties. The roots are thick and hard to pull; some older plants have roots as thick as 2 to 4 inches. As with many plants that reproduce through root suckers, once a piece of this plant is broken off in the soil, it will quickly grow more plants. Add that to the fact that the beautiful bright orange berries also produce new plants. A double whammy!
This vine is considered invasive in Connecticut, Delaware, Illinois, Indiana, Kentucky, Massachusetts, Maryland, Maine, Michigan, Missouri, North Carolina, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Tennessee, Virginia, Vermont, Wisconsin and West Virginia, and at least 14 national parks in the eastern United States, according to the National Park Service and Plant Conservation Alliance Alien Plant Working Group.
The leaves are glossy and elongated with ﬁnely toothed margins. The bright orange roots are easy to distinguish from surrounding root matter. During the early growing season, the leaves intertwine with other plants and are easily overlooked until they have taken control. In areas that are not heavily used, the plants will grow and climb high into trees and shrubs, often adding so much unbalanced weight that trees will topple in wind or snow. Once the small greenish ﬂowers bloom, the fruit sets and turns bright orange by September. This is when it’s easiest to locate and pull these invaders, but it’s also when the plant is vigorous and has set down solid roots. It grows particularly well in disturbed areas and shade, but is also found in ﬁelds, coastal and salt marsh edges, and some sunny sites.
Depending on the size of the infestation, several control methods are recommended. Consult the Plant Conservation Alliance Alien Plant Working Group to choose the method best for your situation.
Bittersweet nightshade (Solanum dulcamara) is another Eurasian intruder. It is a relative of the potato, but that is where the similarities end. All parts of this plant are toxic to humans, livestock, and wildlife and, while mostly non-fatal, the results can be unpleasant. Depending on the region, nightshade is known by many names: bitter nightshade, blue bindweed, blue nightshade, climbing nightshade, dwale, dulcamara, European bittersweet, fellenwort, fevertwig, morel, poisonberry, poisonﬂower, pushion-berry, scarlet berry, skawcoo, snakeberry, tether-devil, wolfgrape, woody nightshade, and deadly nightshade.
Bittersweet nightshade is a woody trailing or climbing vine that reproduces both through root suckering and seeds. The attractive dark green leaves are 2 to 4 inches in size and hairless. Lovely small purple “bird-bill” ﬂowers with yellow anthers bloom in summer, then produce berries which ripen to bright orange or red in the fall. The plant has a very nasty odor when crushed, which helps to identify the plant when it’s not in bloom or bearing fruit.
Found in all states but seven - Arizona, Texas, Arkansas, Mississippi, Louisiana, Alabama, and South Carolina - the plant is on the invasive list for Connecticut, Massachusetts, Maryland, Michigan, Oregon, Pennsylvania, Washington state, and Wisconsin. Bittersweet nightshade invades moist disturbed areas, marshes, ponds, riverbanks, and anywhere else that is unmaintained.
The USDA Forest Service recommendation is to control small areas by hand or digging; if pulling by hand, be sure to wear gloves. For other methods of control, visit the Invasive Plants website.
Take a moment now that the growing season is over and inspect your property for any signs of these unwelcome intruders. If you wait until next year, you could be sorry!
nightshade berries: GNU Free Documentation License, Wikipedia, photo by Guido Gerding mile-a-minute invasion: Matt Reinbold, Creative Commons Attribution 2.0 Generic license on Wikipedia
mile-a-minute leaves: public domain, USFS, on Wikipedia
Toni Leland has been writing for over 20 years. As a spokesman for the Ohio State University Master Gardener program, she has written a biweekly newspaper column and is the editor of the Muskingum County MG newsletter, Connections; she currently writes for GRIT, Over the Back Fence, and Country Living magazines. She has been a gardener all her life, working soil all over the world. In her day job, she scripts and produces educational DVDs about caring for Miniature Horses, writes and edits books about them, and has published five novels.