ANNAPOLIS, MD (November 14, 2005) - A beautiful, fragrant blooming woody vine from Asia, Japanese
honeysuckle (Lonicera japonica) was introduced
into Long Island, NY in 1806 as a garden plant and bank stabilizer.
Although initially slow to spread, by 1912 this perennial vine had
escaped from cultivation, and by 1919 was recognized as a
“ruthless invader.” Japanese honeysuckle has proved
an aggressive and adaptive addition to the U.S. flora and is now
present in the entire continental U.S. except for the Pacific Northwest
and the northern Plains states, as well as in Hawaii and Puerto Rico.
In mid-fall, as native plants lose their leaves, the semi-evergreen
honeysuckle is still highly visible, which is why MISC chose the
species as the November Invader of the Month.
Japanese honeysuckle is a woody vine that climbs by twining around
trees, drapes over lower shrubs, or sprawls across the forest floor. It
has opposite oval to oblong leaves that most often are not toothed or
lobed and have a blunt pointed tip, although as a new seedling,
Japanese honeysuckle may have lobed leaves that look like small white
oak leaves. The familiar fragrant flowers bloom from late April through
June in the mid-Atlantic, but sometimes flowers appear as late as
October. The flowers are creamy white and turn yellow as they age.
Shiny black berries containing two to three dark brown seeds develop in
pairs at the nodes in the fall. Younger vines have tight finely haired
bark, while older vines have rough shredding bark.
A highly adaptable plant, Japanese honeysuckle invades forests, field
edges, disturbed areas, roadsides and floodplains spreading both
vegetatively and by seed. It does not usually invade mature closed
canopy forests, preferring more sunlight, but can establish in
tree-fall gaps or along woodland trails. Once established, it grows
rapidly, scrambling over and smothering native herbs and shrubs.
Twining up trees into the canopy, it can actually girdle adult trees by
twisting so tightly that the supply of water and nutrients is cut off.
Trees are also damaged or killed when the vines are so dense they block
light to their leaves or pull them down by the sheer weight of the
vines. The prolific vine can suppress native tree seedling generation
and reduce native herbaceous growth. It competes directly above-ground
for light and below-ground for nutrients and space. The seeds are eaten
by both birds, including robins, turkeys, quail, bluebirds and
goldfinches, and mammals, which furthers its spread. White-tailed deer
browse on it, and may contribute to its spread by dispersing the fruit.
In most of Maryland, Japanese honeysuckle is semi-evergreen, and can
even hold its leaves throughout the entire winter. It can grow, slowly,
at temperatures just above freezing. These characteristics enable the
plant to continue to photosynthesize and grow well into the winter,
long after native deciduous vines such as Virginia creeper and grapes
have lost their leaves. It also gives honeysuckle a jump-start in the
spring, when the plant begins to grow as soon as temperatures begin to
rise, before native leaf out.
Japanese honeysuckle, including the especially aggressive variety
Hall’s honeysuckle (Lonicera japonica
var. halliana), is still widely sold as a garden ornamental or for
covering walls, fences and steep banks. It can be a beautiful garden
plant, but once escaped, becomes a damaging invader in natural areas.
The best way to control Japanese honeysuckle is not to let it get
established in the first place. Small plants can be pulled or grubbed
out relatively easily. Larger sprawling vines may be removed with a
weed wrench or similar tool. However, other tactics are needed for
larger and more established infestations, including use of commonly
available herbicides such as glyphosate (RoundUp, Rodeo, etc) applied
any time from spring through fall when the plant is actively growing.
For additional information about specific control tactics go to:
which is part of the National Park Service's "Weeds
Gone Wild" web site.
photos available electronically on request.
Tim McDowell, East Tennessee State University
For more information about Japanese honeysuckle and other Invasive
Species of Concern, visit www.mdinvasivesp.org