DescriptionAsiatic bittersweet is a non-native woody vine with yellow fruits which split to reveal showy bright red seeds. It is also commonly referred to as Oriental bittersweet. This highly invasive species entwines its round, brown stems about other plants and structures, climbing as high as sixty feet. Approximately two weeks after autumn foliage's peak, the leaves turn golden-yellow and are easily sighted. Diagnostic informationRoots: outer surface is characteristically bright orange. Stem and branches: round and brown. Flowers: small, greenish-yellow, with 5 sepals and 5 petals, clustered in the axil of the leaves. Fruit: 1/4" diameter, change from green to bright yellow as mature, bright scarlet arils. Leaves: 3/4" to 4-3/4" long and 5/8" to 3-1/4" wide, margin is crenate to serrate, base is cuneate to obtuse, tip is acute to rounded, change from green to golden-yellow as mature. HabitatIn its native Asia, this species dominates lowland slopes and thickets. Here in North America, Asiatic bittersweet is extremely successful in almost any habitat type, such as disturbed edges, abandoned fields, along coast, and the edge of salt marshes. It prefers utility corridors, fence rows, railroads, and roadways (for example, it is prolific along the Merritt Parkway). Seasonal CycleAsiatic bittersweet is a deciduous perennial plant. There are typically separate male and female plants, which bloom in May and June. Bees aid in pollination. The fruit (on the female plant) ripens by September and remains on the vine through winter. Numerous bird species, such as black-capped chickadee, northern mockingbird, European starling (non-native), and blue jay, small mammals, and human activity (such as composting ornamental cuttings) widely disperse the Asiatic bittersweet's seeds. Rootsuckering, the ability to send up shoots from the roots, contributes to the vine's high density once established at a site. DistributionAsiatic bittersweet is native to temperate East Asia (Japan, Korea, and China). Introduced to North America in the mid-nineteenth century, it quickly became established from Louisiana to Maine. Asiatic bittersweet reached Connecticut as early as 1916 as an ornamental and is now found throughout the state. ThreatDue to its high reproductive rate, long-range seed dispersal, and rootsuckering abilities, Asiatic bittersweet can quickly disperse through an entire area, threatening upland meadows, thickets, young forests, and beaches alike. Growth of native vegetation is extremely limited beneath bittersweet's dense shade, and it tends to strangle small trees and shrubs by growing around their stems, constricting the flow of the plant's fluids. Many supporting plants also succumb to wind and ice storms with the added weight of the vine. Asiatic bittersweet also has the capacity to hybridize with the native American bittersweet (Celastrus scandens), cross-pollinating to the extent of modifying the genetic differences between the two species. ControlThe Nature Conservancy and project partner the Connecticut Agricultural Experiment Station recently conducted research on the control of Asiatic bittersweet at Bluff Point, in Groton, funded by the DEP License Plate Fund (project completed in Fall of 2006). Included in this research were herbicide treatments, applied to the basal bark of vines, as well as applications to cut stumps, near ground level. These applications were done using a foam paint brush, not from a spray. Different concentrations of the chemicals glyphosate (Roundup is one product name) and triclopyr (Brush-B-Gon) were used for each treatment. Other Points of InterestAsiatic bittersweet is similar in appearance to the native species American bittersweet. Asiatic bittersweet is distinguished from American bittersweet by the fact that its fruit and flowers are located in clusters of three to seven in the axil of the leaves (between the leaf and the stem). American bittersweet's fruit and flowers are located at the branch tips only. It is very important for land managers, naturalists, and gardeners to distinguish between the native species and the invasive species in any control efforts. Asiatic bittersweet was planted for wildlife food and cover, cultivated to use the fruit-covered vines for decorations, and employed in soil erosion control. Nature picture credits (top to bottom, left to right): Photo © Chris Evans, River to River CWMA, Bugwood.org (Bright Red Seeds of the Asiatic bittersweet (Celastrus Orbiculatus)); Photo © Chris Evans, River to River CWMA, Bugwood.org (Asiatic bittersweet (Celastrus Orbiculatus)). |
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