Bulletin #2507, Shrubby Honeysuckles
Maine Invasive Plants
Developed by the Maine Natural Areas Program and University of Maine Cooperative Extension
Threats to Native Habitats
Shrub honeysuckles can rapidly invade and degrade native plant communities. They form a dense layer that shades the ground, interfering with the growth of many native woody and herbaceous species, including rare plants. The ground under a honeysuckle thicket is often void of other vegetation. Shrub honeysuckles leaf out earlier than native species and they retain their leaves longer into the fall, giving them a competitive edge. Their success on high pH, dry, exposed soils has made them a threat to some of the Northeast’s unique limestone plant communities. The fruit of these shrubs is eaten by common birds, which helps spread the seed into new locations and makes the shrub even more difficult to control.
Bush honeysuckles are upright deciduous shrubs that grow from a few feet to as high as 16 feet. The branches are widely spreading, with the older ones being hollow. The oval to oblong leaves are from 1 to 2½ inches long and are arranged in pairs on the stem. The flowers are tubular and occur in pairs. The fruit is a many-seeded red, orange or yellow berry. Tartarian honeysuckle has hairless leaves and flowers that are pink or white, and that do not turn yellow with age. Morrow honeysuckle has fuzzy or downy leaves and white flowers that turn yellow with age. Hybrid honeysuckle is a cross between Tartarian and Morrow honeysuckle and generally has features common to both but is capable of growing substantially taller. Care should be taken not to mistake the common native fly-honeysuckle (Lonicera canadensis) for these non-natives. The native fly-honeysuckle can be distinguished from non-natives by its pith. The native honeysuckle has solid pith—spongy tissue inside the stem—while non-native honeysuckles have hollow pith (cut stem lengthwise to see). Also, the native fly-honeysuckle flowers much earlier in spring, while the others flower in June.
Bush honeysuckles can be aggressive colonizers of abandoned agricultural fields, hedgerows, and edges of forests and wetlands, but they can also be found in forests, especially where there has been disturbance and the soils are limey. They prefer open locations but can tolerate moderate shade and can grow in soils ranging from moist to very dry.
Tartarian honeysuckle is native to central and eastern Russia, where it is found in a wide range of habitats and can tolerate desiccating winds, near-drought conditions, and temperatures ranging from -50 to +110 degrees F. Morrow honeysuckle is native to Japan, where it also occurs in a wide range of habitats and lives in a climate similar to the Atlantic coast of the U.S. Generally, Tartarian honeysuckle is found in dry, exposed sites and Morrow honeysuckle is found in wetter sites. Each of the honeysuckles listed is highly invasive. Shrub honeysuckles are now naturalized (established and reproducing in the wild) throughout much of the northeastern United States. As recently as the 1980s they were promoted for their wildlife values, ornamental use, and soil stabilization. In Maine, shrub honeysuckles have been documented in every county except Franklin and Piscataquis.
The best method of control is to prevent non-native shrubby honeysuckles from becoming established. These plants should be removed as soon as possible if they are found colonizing an area. Small infestations can be cleared by hand using a shovel or hoe, provided the entire root is removed. Larger colonies have been controlled by various combinations of repeated treatments of mechanical control, burning, or applying a glyphosate herbicide. If cutting is included as part of a treatment, it should be done in early spring and in late summer or early fall. Cutting of plants results in resprouting, but is effective in temporarily reducing seed production. Seedlings are easily pulled. Treatment by prescribed burning is most effective if conducted during the growing season. Control methods may need to be repeated for three to five years to inhibit resprouting and to exhaust the seedbank.
Josselyn Botanical Society of Maine. 1995. Checklist of the Vascular Plants of Maine, Third Revision. Orono, ME: Maine Agricultural and Forest Experiment Station.
Converse, C. K. 1984. Element Stewardship Abstract for Lonicera spp. Arlington,VA: The Nature Conservancy in collaboration with the International Network of Natural Heritage Programs and Conservation Data Centers. Natural Heritage Databases.
The Nature Conservancy of Vermont. 1998. Invasive Exotic Fact Sheet: Shrubby Honeysuckles. Montpelier, VT.
Gleason, H.A. and A. Cronquist. 1991. Manual of Vascular Plants of Northeastern United States and Adjacent Canada. New York: New York Botanical Garden.
For more information or for a more extensive list of references on invasive species contact:
Department of Conservation
#93 State House Station
Augusta, ME 04333-0093
Lois Berg Stack
University of Maine Cooperative Extension
495 College Avenue
Orono, ME 04469
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