Invasive Species: Pesky Plants by Mark Boshnack
Invasive Bittersweet a Bitter Pill
Some invasive species have a similar looking native counterpart. This can complicate efforts by those seeking to root out the problem, the invasive form. The Asiatic (Oriental) bittersweet, Celastrus orbiculatus, was introduced to this country in the late 1800s as an ornamental plant for erosion control. It has an attractive appearance in the fall, with red berries enclosed by a yellow-orange capsule. The invasive species is native to Eastern Asia, Korea, China and Japan, according to the U.S. Department of Agriculture. In the United States it is most common in New York, coastal Connecticut, and the southern Appalachian Mountains. It is one of those pesky plants that needs to be eliminated from our landscape. The related, American bittersweet, Celastrus scandens, is a native.
The woody vine of the invasive form grows vigorously and smothers native vegetation, according to John Thompson, director of the Catskill Regional Invasive Species Partnership. Asiatic bittersweet is considered a “generalist,” meaning that it is found in a variety of habitats including fields, hedgerows, wetland margins, forest edges and open woodlands. Although it does best in open sunny areas, it is shade tolerant, which allows it to invade forests. It is an aggressive vine that uses other plants as scaffolding, and creates dense, tangled swaths that shade out and smother other plants. It can do substantial damage to trees by girdling them and by weighing down limbs, which can result in the eventual death of the native plant.
The Asiatic bittersweet is spread primarily through the dispersal of its seeds by birds which feed on its berries. CRISP can be helpful with such issues as early detection and rapid response to an invasive species in the region. The invasive vine is much more aggressive than the native species, Thompson said. In addition, when birds and animals eat the berries of the invasive form, the fruit provides less nutritional value than the native counterpart.
There are several ways to distinguish the invasive form. The native, American bittersweet has a longer and narrower leaf than does the invasive counterpart. The leaf of the native is also more deeply toothed. In addition, the native produces flowers and fruit at the stem tips, while the Asiatic bittersweet produces flowers and fruit at the leaf axils, where the leaf joins the branch. According to the Essex County Greenbelt Association, another way to tell them apart is that the invasive bittersweet has smooth stems, while the native bittersweet has blunt thorns.
Asiatic bittersweet is prohibited from being introduced, sold, propagated, transported or purchased in New York State. To eradicate the invasive bittersweet, the CRISP website (www.catskillinvasives.com) recommends: “Consistently cutting vines and pulling up root shoots several times a year for several consecutive years will eventually weaken plants. Alternatively, careful application of glyphosate on cut stems can be done in the fall.” People who find Asiatic bittersweet are asked to report its location at www.iMapInvasives.org.
Mark Boshnack is an Otsego Master Gardener volunteer.
