Lonicera maackii, the Amur honeysuckle, is a species of honeysuckle in the family Caprifoliaceae that is native to temperate western Asia; specifically in northern and western China south to Yunnan, Mongolia, Primorsky Krai in southeastern Siberia, Korea, and, albeit rare there, central and northern Honshū, Japan.
Lonicera maackii is a listed endangered species in Japan. It has escaped from cultivation and naturalized in New Zealand and the eastern United States; in the woodlands of the U.S. it is a significant invasive species.
The plant is a large, deciduous shrub that grows a maximum of 6 m tall with stems of a maximum of 10 cm in diameter. The leaves are oppositely arranged, 5–9 cm long and 2–4 cm broad, with an entire margin, and with at least some rough pubescence.
The flowers are produced in pairs, and commonly several pairs are produced together in clusters; they are 2 cm long, have two lips, begin white and later turn yellow or pale orange in color; they bloom from middle of spring to early summer. The fruit is a bright red to black, semi-translucent berry, 2–6 mm in diameter, that contains numerous small seeds; they ripen in autumn and are eaten by birds, which disperse the seeds in their droppings.
The species name "maackii" is derived from Richard Maack, a Russian naturalist of the 19th century. Its common name "Amur honeysuckle" is from its native range surrounding the Amur River, which demarcates the border between Siberia and Manchuria.
- Some Internet sources name the species authority as "(Rupr.) Herder", but the correct authority is "(Rupr.) Maxim".
Amur honeysuckle is cultivated as an ornamental plant for its attractive flowers and as a hedge. Many cultivars have been selected for horticulture, including "Erubescens" with pink flowers and "Rem Red" with an erect form. The plant is adaptable and flourishes in a wide range of conditions. In the United States, it was planted to control erosion and to form hedges. It readily self-propagates via birds dispersing its seeds, and quickly spreads into habitats for which it has no community connectivity. It does not naturalize, it invades.
The flowers are sometimes savored by children, who remove blossoms and pull off their bottoms so as to suck out the sweet nectar in the centers. However, the berries are mildly poisonous to humans and therefore should not be consumed.
Because of the invasive nature of this species, regardless of whether it is banned locally, it may be imprudent to cultivate Amur honeysuckle in climates similar to those where the species has invaded, e.g. eastern North America.
Possible alternative shrubs that are also fast growing, shade tolerant, and deciduous, but not invasive in eastern US include:
More native shrubs for use the Midwestern United States are listed in the pamphlet Curse of the Bush Honeysuckles!.
Invasive nature and remedies
Because of its well-documented invasiveness, propagation of this plant is illegal or controlled in some of the United States, where it is an alien species. The species is named "invasive, banned" in Connecticut, "prohibited" in Massachusetts, as an invasive species in Tennessee, as an invasive species in Ohio, as a "Class B noxious weed" in Vermont, and as an invasive species in Wisconsin.
It has been suggested that plants growing outside their native range, in eastern Asia, should be removed and replaced by non-invasive alternatives.
In the understories of deciduous woodlands of the eastern United States it forms dense thickets, the shade of whose canopies prevent the growth of native shrubs, juvenile trees, and wild flowers. Uncontrolled, these growths result in almost monocultural thickets of Amur honeysuckle. The species gravely jeopardizes not only the diversity of the invaded ecosystems but even the regeneration of woodlands, because it reduces the growth and diversity of native seedlings. Additional studies indicate that it negatively affects birds and tadpoles. Even if its shrubs are removed, the affected habitat may not recover absent substantial restoration effort.
A study conducted in the vicinity of St. Louis, Missouri in 2010 indicated that the plant increases the risk of tick-borne diseases such as Erlichiosis and Lyme disease in suburban natural areas by attracting deer and consequently increasing the presence of infected ticks. Furthermore, experimental removal of the plant was shown to reduce deer activity and the number of infected ticks by shifting ticks' blood meals from deer.
Control and eradication
The species is controlled by cutting, flaming, or burning the plant to the level of its roots and repetition of this in two-week increments until the nutrient reserves in the roots are depleted. To ensure eradication, herbicide may be applied to freshly cut stumps. Control by prescribed burning has been found to be most effective during the phase of seed dispersal in late summer and early autumn.
It can also be controlled by annual applications of glyphosate that thoroughly saturate the foliage, or by grubbing the shallowly rooted juvenile plants, but these two methods increase labor cost and disrupt the soil.
- "The Plant List: A working list of all plant species". Retrieved 7 December 2014.
- "Lonicera maackii". Germplasm Resources Information Network (GRIN). Agricultural Research Service (ARS), United States Department of Agriculture (USDA). Retrieved 2 January 2018.
- "Red List of Threatened Plants of Japan". Ministry of the Environment (Excel spreadsheet). Government of Japan.
- "Lonicera maackii (with map)". Red Data Book (Japan) (in Japanese). Archived from the original on 15 June 2011; "Google translation".
- "Amur honeysuckle" (PDF). USDA Forest Service. Weed of the Week Fact Sheet. United States Department of Agriculture (USDA).
- "L. maackii". Pocket Gardener. Ohio State University. Archived from the original on 14 July 2007.
- Huxley, A., ed. (1992). New RHS Dictionary of Gardening. Macmillan. ISBN 0-333-47494-5.
- "Lonicera maackii in Missouri". Missouriplants.
- "Annotated bibliography of primary research on invasive qualities of L. maackii in the U.S.A." National Biological Information Infrastructure. Knoxville, TN: University of Tennessee. Archived from the original on 13 May 2007.
- "L. maackii". Department of Horticulture. Plant Database. University of Connecticut. Archived from the original on 10 May 2007.
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- "Curse of the Bush Honeysuckles!" (PDF). mdc.mo.gov. Missouri Department of Conservation.
- "L. maackii". USDA Plants Database. United States Department of Agriculture (USDA).
- Gorchov, David L.; Trisel, Donald E. (1 May 2003). "Competitive effects of the invasive shrub, Lonicera maackii (Rupr.) Herder (Caprifoliaceae), on the growth and survival of native tree seedlings". Plant Ecology. 166 (1): 13–24. doi:10.1023/A:1023208215796. S2CID 41965189.
- Schmidt, Kenneth A.; Whelan, Christopher J. (1 December 1999). "Effects of Exotic Lonicera and Rhamnus on Songbird Nest Predation". Conservation Biology. 13 (6): 1502–1506. doi:10.1046/j.1523-1739.1999.99050.x.
- Watling, J.I.; Hickman, C.R.; Lee, E.; Wang, K.; Orrock, J.L. (1 January 2011). "Extracts of the invasive shrub Lonicera maackii increase mortality and alter behavior of amphibian larvae". Oecologia. 165 (1): 153–159. doi:10.1007/s00442-010-1777-z. PMID 20938785. S2CID 7347009.
- Rodewald, A.D.; et al. (2015). "Does removal of invasives restore ecological networks? An experimental approach". Biological Invasions. 17 (7): 2139–2146. doi:10.1007/s10530-015-0866-7. S2CID 14654835.
- Allan, Brian F.; Dutra, Humberto P.; Goessling, Lisa S.; Barnett, Kirk; Chase, Jonathan M.; Marquis, Robert J.; et al. (26 October 2010). "Invasive honeysuckle eradication reduces tick-borne disease risk by altering host dynamics". Proceedings of the National Academy of Sciences. 107 (43): 18523–18527. doi:10.1073/pnas.1008362107. PMC 2973004. PMID 20937859.
- Craves, J.A. (2017). "Native birds exploit leaf-mining moth larvae using a new North American host, non-native Lonicera maackii". Ecoscience. 24: 81–90.
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