SPECIES CHARACTER
Description
Japanese honeysuckle is a semi-evergreen vine in Illinois, often holding its
leaves late into winter. Leaves are ovate and 1.5-3.2 inches (4-8 cm) long.
White to yellow tubular flowers form in pairs in the leaf axils and occur from
May-June. The 2-3 seeded fruits are small and black.
Similar Species
Japanese honeysuckle is separated easily from the native honeysuckle vines by
its leaves. Leaves near tips of the vines of Japanese honeysuckle are opposite
and not united, while leaves of native honeysuckles (3 species) are united at
the base, forming a single leaf surrounding the stem. Japanese honeysuckle
should be accurately identified before at tempting any control measures. If
identification of the species is in doubt, the plant's identity should be
confirmed by a knowledgeable individual and/or by consulting appropriate books.
Distribution
Japanese honeysuckle is native to Japan, introduced to the U.S. in 1806 for
horticultural ground-cover purposes. It was slow to escape and did not become
widely established over the eastern U.S. until the early 1900's. It presently
occurs as far north as Illinois and Michigan. It has rapidly spread into many
open natural communities in the southern 2/3 of Illinois. It has not been found
to be a serious pest north of Peoria, although it is recorded from 10 northern
Illinois counties. Bitter cold winter temperatures appear to limit this species
somewhat. Nonetheless, this vine is becoming increasingly common in central
Illinois.
Habitat
Japanese honeysuckle readily invades open natural communities, often by seed
spread by birds. An aggressive colonizer of successional fields, this vine
also will invade mature forest and open woodlands such as post oak flatwoods and
pin oak flatwoods. Forests with either natural or unnatural openings are often
invaded by Japanese honeysuckle when birds drop seeds into these light gap
areas. Deep shading reduces the amount of invasion.
Life History
Japanese honeysuckle climbs and drapes over native vegetation, shading it out.
It is capable of completely covering herbaceous and understory plants, and
climbing trees to the canopy. The semi-evergreen condition of this honeysuckle
allows for growth both prior to and after dormancy of other deciduous plants.
The prolific growth covers and smothers vegetation present including understory
shrubs and trees in forested communities. Although this prolonged growth period
is beneficial to the plant, it is also beneficial in controlling the plant.
Vegetative runners are most prolific in the open sun and will resprout where
touching the soil, forming mats of new plants. This honeysuckle will display
little growth under moderate shade. In deep shade, runners develop but often
die back. Flowering and seed development are heaviest in open-sun areas.
Seedling establishment and growth is slow in the first 2 years of development of
a new honeysuckle colony.
Effects Upon Natural Areas
This aggressive vine seriously alters or destroys the understory and herbaceous
layers of the communities it invades, including prairies, barrens, glades,
flatwoods, savannas, floodplain and upland forests. Japanese honeysuckle also
may alter understory bird populations in forest communities.
Current Status
Japanese honeysuckle is categorized as an exotic weed under the Illinois Exotic
Weed Control Act of 1987. As such, its commercial sale in Illinois is
prohibited.
CONTROL RECOMMENDATIONS
RECOMMENDED PRACTICES IN HIGH-QUALITY NATURAL COMMUNITIES, BUFFER, AND
SEVERELY DISTURBED SITES
Initial effort in areas of heavy and light infestation
Efforts to control Japanese honeysuckle infestations have included the following
methods: mowing, grazing, prescribed burning and herbicides. While grazing and
mowing reduces the spread of vegetative stems, prescribed burns or a combination
of prescribed burns and herbicide spraying appears to be the best way to
eradicate this vine.
In fire-adapted communities, spring prescribed burns greatly reduced Japanese
honeysuckle coverage and crown volume. Repeated fires reduced honeysuckle by as
much as 50% over a single burn. A previously burned population of honeysuckle
will recover after several years if fire is excluded during this time. By
reducing honeysuckle coverage with fire, refined herbicide treatments may be
applied, if considered necessary, using less chemical.
Because Japanese honeysuckle is semi-evergreen, it will continue to
photosynthesize after surrounding deciduous vegeta tion is dormant. This
condition allows managers to detect the amount of infestation, and allows for
treatment of the infestation with herbicides without damage to the dormant
vegetation.
Glyphosate herbicide (tradename Roundup) is the recommended treatment for this
honeysuckle. A 1.5-2% solution (2-2.6 oz of Roundup/gallon water) applied as a
spray to the foliage will effectively eradicate Japanese honeysuckle. The
herbicide should be applied after surrounding vegetation has become dormant in
autumn and before a hard freeze (250F). Roundup should be applied carefully by
hand sprayer, and spray coverage should be uniform and complete. Do not spray
so heavily that herbicide drips off the target species. Retreatment may be
necessary for plants that are missed because of dense growth. Although
glyphosate is effective when used during the growing season, use at this time is
not recommended in natural areas because of the potential harm to nontarget
plants. Glyphosate is non-selective, so care should be taken to avoid contacting
nontarget species. Nontarget plants will be important in recolonizing the site
after Japanese honeysuckle is controlled.
Crossbow, a formulation of triclopyr and 2,4-D, is also a very effective
herbicide that controls Japanese honeysuckle. Crossbow should be mixed
according to label instructions for foliar application and applied as a
foliar spray. It may be applied at dormant periods, like glyphosate, and
precautions given above for glyphosate should be followed when using Crossbow.
Either herbicide should be applied while backing away from the treated area to
avoid walking through the wet herbicide. By law, herbicides only may be applied
according to label instructions and by licensed herbicide applicators or
operators when working on public properties.
Maintenance control
In fire-adapted communities, periodic spring burning should control this
species.
FAILED OR INEFFECTIVE PRACTICES
Mowing limits the length of Japanese honeysuckle vines, but will increase the
number of stems produced.
Grazing may have the same effects as mowing, but is less predictable due to
uneven treatment given by browsing animals.
Herbicides that have given poor control results or that are more persistent in
the environment than other types are picloram, annitrole, aminotriazole,
atrazine, dicamba, dicamba & 2,4-D, 2,4-D, DPX 5648, fenac, fenuron, simazine &
triclopyr.
REFERENCES
Barden, L.S. and J.F. Matthews. 1980. Change in abundance of honeysuckle (Lonicera japonica) and other ground flora after prescribed burning of a Piedmont pine forest. Castanea 45:257-260.
Sather, N. 1987. The Nature Conservancy's element stewardship abstract, Japanese honeysuckle (Lonicera japonica). 11 pp.
United States Department of Agriculture, Agricultural Research Service. 1970. Selected Weeds of the United States. Agricutural Handbook No. 366. U.S. Government Printing Office, Washington D.C.
PERSONAL COMMUNICATIONS
Stritch, L. 1988. Division of Natural Heritage, Illinois Department of Conservation, Springfield, Illinois.
West, A. 1988. Division of Natural Heritage, Illinois Department of Conservation, Springfield, Illinois.
Written for the Illinois Nature Preserves Commission by:
Randy Nyboer
Illinois Department of Conservation
Dearborn Hall
205 E. Seminary Street
Mt. Carroll, Illinois 61053