Seasonal cycle: Asiatic 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.
Distribution: Asiatic 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.
Control: Due 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 American bittersweet (Celastnls scandens), cross-pollinating to the extent of
modifying the genetic differences between the two species.
The Connecticut College Arboretum, Connecticut Department of
Transportation, and The Nature Conservancy are working to improve the control and
management of Asiatic bittersweet. Low patches can be removed by cutting the vine and
applying triclopyer herbicide (the active ingredient in Ortho's Brush-BGone) to the
regrowth a month later. For taller patches, the main stems can be cut and triclopyer
herbicide applied immediately to the cut stem and to any subsequent regrowth. Care must be
taken to protect the remnant native plant species when cutting to ensure that they
revegetate the area. Asiatic bittersweet has a substantial seed bank, and successful
removal of the species requires perseverance through two or three years. The Nature
Conservancy's Connecticut Chapter currently manages Asiatic bittersweet at its Griswold
Point Preserve.
Other points of interest: Asiatic 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.
Additional information sources:
Gray 's Manual of Botany. Eighth edition, corrected printing. New York 1970.
D. Van Nostrand Company, M. Fernald.
Manual of Vascular Plants of Northeastern United States and
Adjacent Canada. Gleason and A. Cronquist. The New York Botanical Garden, Bronx 1991.
Second edition. H.
Diagnostic information: Roots: 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.
This fact sheet has been prepared by The
Nature Conservancy Connecticut Chapter.
