Wednesday, March 1, 2017

Invasive Species Highlight - Oriental Bittersweet

We often hear Kudzu vine referred to as the vine that ate the south. Well, we may have the vine that eats Pennsylvania, Oriental bittersweet (Celastrus orbiculatusis). It is becoming more and more of a problem, a problem that is not easily solved.

Minnesota Dept. of Agriculture
As I sat on my favorite deer stand, in the woods of central Pennsylvania, this past hunting season I began to pick them out. The climbing vine and the orange seed pods of Oriental bittersweet were easily recognized through my binoculars. I mentally marked the vines locations with the intent of coming back after the season and cutting them at the ground line to free the trees from its strangling grip. I plan to treat the freshly cut stumps with a systemic herbicide to prevent re-sprouting.

Learn to identify this damaging invasive vine before it takes over your woodlot…..if it hasn’t already. It is important to get control of this vine early before it has a chance to spread, and it will spread. Those bright orange berries found on the female vines are readily eaten by birds and transported great distances. Once under control, a scouting and maintenance program is an absolute must.

Oriental bittersweet is a deciduous, climbing, woody vine that can grow up to 60 feet in length and up to four inches in diameter. Native to Korea, China, and Japan, it was introduced in the 1860s as an ornamental. It quickly naturalized in many areas. Bittersweet rapidly grows into the tops of trees, overtoping existing vegetation, shading and eventually killing saplings and trees. Vines can cause structural damage by girdling branches and trunks and even toppling trees.

The finely toothed, round leaves are glossy and alternately
arranged. The plant flowers in the spring and bears clusters of small greenish flowers that emerge from the leaf axils. The globular green to yellow fruit ripens in the fall. Upon ripening, the orange fruit splits open revealing three red-orange, fleshy berries. The berries remain on the vine through the winter. The seed remains viable in the soil for years.

Oriental bittersweet grows in fields and woodlands, around old home sites, along roadsides, and hedgerows. It thrives in moist to semi-moist soils but has also been found growing vigorously in sand dunes along coastal areas. This vine tolerates shade, but prefers full sun. Dense, smothering stands may form under the right light and moisture conditions.

Mechanical control, such as pulling or mowing, can be used to remove light infestations of small plants. When soil moisture is high, vines can be pulled by hand. Take care to remove all root fragments as bittersweet will re-sprout. In old fields, mowing two to three times a year stimulates root suckering.

Cut and treat stumps with 50% glyphosate
To successfully control infestations of this vine a two-step approach is recommended. First, remove the aerial portions by “window” cutting the vines any time of year. Window cutting means the vines are cut at eye level and again close to the ground. This allows you to visually see what vines have been cut as you move through an area. It is optional to treat the stumps at this time with a systemic herbicide (e.g., glyphosate) or to leave them. The vines will re-sprout unless an herbicide is applied to the cut stump.

The second step is to treat the re-growth. Even if the stumps were chemically treated the root system will likely send up sprouts. After a growing season, the re-growth will be like a small shrub rather than a climbing vine. The foliage can be successfully managed with an herbicide (e.g. glyphosate or triclopyr amine). For root suckering species, like bittersweet, it is important to treat foliage late in the growing season to enhance herbicide translocation to roots.

It is important not to confuse the invasive Oriental bittersweet vine with its native look-alike, American bittersweet (Celastrus scandens). American bittersweet has flowers and fruits at the ends of its branches, rather than in the axils of the leaves. Because native bittersweet is beneficial, consult a natural resource professional to properly identify bittersweet before implementing control plans.

To view an excellent 4 minute video by the University of Minnesota Extension click on the below link.

For a Penn State Invasive Plant Species Management fact sheet click the below link.

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