Bush Honeysuckles: Morrow's and Amur Honeysuckle
[Lonicera morrowii Gray and L. maackii (Rupr.) Maxim.]
DESCRIPTION
The two species of honeysuckle shrubs planted (Morrow's
and Amur) that cause the more frequently observed invasive problems will
be referred to collectively as bush honeysuckles. Bush honeysuckles grow
to heights of 6-20 feet (1.8-6 meters). They are deciduous, with opposite,
entire leaves, and often the older branches are hollow. Differences between
individual species of non-native honeysuckles are dependent on the presence
of pubescence on leaves and flowers and the length of flowers and their
stems. Bush honeysuckles flower during May and June. Amur and Morrow's
honeysuckle flowers are both white, fading to yellow as they age. Fruits
are red and are found in pairs in the axils of the leaves.
SIMILAR SPECIES
Bush honeysuckles are easily separated from native honeysuckle species by their stout, erect shrub growth. All native species are "woody twiners" that are vine-like in nature. Japanese honeysuckle, an exotic, is also a twiner. See page 63 for its description. Native honeysuckle species are grape honeysuckle (Lonicera reticulata), yellow honeysuckle (Lonicera flava), and limber honeysuckle (Lonicera dioica). However, a shrub should be accurately identified as a bush honeysuckle before attempting 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
Bush honeysuckles are native to Asia. These species were introduced to North America in the late 1800s and 1900s. Morrow's honeysuckle and Amur honeysuckle are now known from northern and central Missouri. Although the distribution of these plants is predominately near larger urban areas, where they are used as ornamentals, rural infestations are common when the species are used to improve wildlife habitat.
HABITAT
Bush honeysuckles have a broad tolerance to a variety of moisture regimes and habitats. Most natural communities are susceptible to invasion by one or both of the species. Often the source of the invasion comes from a planting or from a highly disturbed successional community in which the honeysuckle has flourished. Both Morrow's and Amur honeysuckle frequently escape into woodlands, and Morrow's honeysuckle is sometimes found along roadsides as well. Wetlands, prairie, and forested communities are all affected. Habitat disturbance appears to facilitate introduction of these species, but native habitats without previous disturbance are also subject to invasion.
LIFE HISTORY
The spread of bush honeysuckle is generally accomplished by birds. Fruits are consumed readily upon ripening during summer. Bush honeysuckle plants commonly are found growing under tall shrubs or trees that act as perch areas for birds. Seeds appear to need a cold stratification period in order for the seed to break dormancy. Seedlings establish in areas of sparse herbaceous vegetation and can tolerate moderate shade. It is suspected that bush honeysuckles may produce allelopathic chemicals that enter the soil and inhibit the growth of other plants, preventing native plants from competing with the shrub. Shading by bush honeysuckle may also limit the growth of native species. Bush honeysuckles leaf out before many native species and hold their foliage until November.
EFFECTS UPON NATURAL AREAS
Bush honeysuckles will invade a wide variety of native habitats with or without previous disturbances. Affected natural communities in Illinois include: lake and stream banks, marsh, fens, sedge meadow, wet and dry prairies, savannas, floodplain and upland forest. Mesic upland and bottomland forests in Missouri are known to contain invasive stands.
Control Recommendations
Recommended Practices in Natural Communities of High Quality
Control measures may enlist one or more of the following techniques: prescribed burning, hand pulling of seedlings, cutting, and herbicide treatments. A recently introduced pest, the European Honeysuckle aphid, somewhat controls flower and fruit production in some of the bush honeysuckles. Heavy infestations cause tips of branches to form "witches brooms' or deformed twigs. This often greatly reduces fruit production. Native ladybug beetles, however, have been noted to control this aphid.
In fire-adapted communities, spring prescribed burning will kill seedlings and kill the tops of mature plants. Bush honeysuckles readily resprout and repeated fires are necessary for adequate control. It may be necessary to burn annually or biennially for five years or more for effective control.
Seedlings may be hand-pulled when soils are moist. All of the root should be removed or resprouting will occur. Physical removal by hand-pulling smaller plants or grubbing out large plants should not be used in sensitive habitats. Open soil and remaining root stocks will result in rapid reinvasion or resprouting of honeysuckles and other exotics
Bush honeysuckle stems can be cut at the base with brush-cutters, chainsaws or hand tools. After cutting, a 20% solution of glyphosate should be applied to the cut stump either by spraying the stump with a low pressure hand-held sprayer or wiping the herbicide on the stump with a sponge applicator to prevent resprouting. Glyphosate is available under the tradenames Roundup and Rodeo, products manufactured by Monsanto. While the Roundup and Rodeo labels recommend a 50-100% concentration of herbicide for stump treatment, a 20% concentration of Roundup has proven effective. It is not known if this lesser concentration is effective for Rodeo also. Rodeo can be used in wetlands and over open water, but Roundup is only labeled for use in non-wetlands. Herbicides should be applied to the cut stump immediately after cutting for best results. Application in late summer, early fall, or the dormant season has proven effective. Some resprouting may occur with a follow up treatment being necessary. Glyphosate is non-selective so care should be taken to avoid contacting non-target plants. The wood of bush honeysuckles is very tough and easily dulls powertool blades. Underplanting of native species following honeysuckle removal may be necessary to reestablish a desirable composition of groundcover, shrubs, and understory trees. This may also minimize the risk of reinvasion by shrub honeysuckles and other exotics.
Recommended Practices on Lands Other Than High-Quality Natural Areas
Methods given above for high-quality natural communities are also effective and preferred on buffer and disturbed sites. When an area with bush honeysuckle lacks sufficient fuel to carry a fire, herbicides may be necessary to obtain control.
In dry, upland areas, a foliar spray of 1% Roundup (glyphosate) will control seedlings. A one and one half % foliar spray of Roundup just after plant blooming in June will control mature shrubs. Application should occur from late June to just prior to leaf color changes in fall. The herbicide should be applied while backing away from treated areas so as not to walk through the wet herbicide.
In areas near water, a foliar spray of 1% Rodeo (glyphosate) with Ortho-X27 spreader, will control seedlings. Application should occur from late June to just prior to changes in leaf color in the fall. Foliar application of a one and one-half % solution of Rodeo (2 oz. Rodeo/gallon clean water) will kill mature plants if all foliage is sprayed. This control method usually requires less labor but more herbicide.
In addition, Krenite controls bush honeysuckle when applied according to label instructions. Any treatment should be rechecked in following years for reinvasion. Glyphosate is a nonselective herbicide and care should be taken to avoid contacting nontarget plants with herbicide. Do not spray so heavily that herbicide drips off the target species. By law, herbicides only may be applied according to label instructions.
Failed or Ineffective Practices
The herbicide Garlon does not control bush honeysuckle.
Adapted from material written for the Illinois Nature Preserves Commission
by:
Randy Nyboer
Illinois Department of Conservation
Dearborn Hall
205 E. Seminary Street Mt. Carroll, Illinois 61053
