Lonicera japonica, the Japanese honeysuckle or suikazura (スイカズラ／吸い葛 in Japanese; jinyinhua in Chinese; 忍冬 in Chinese and Japanese, 인동 or 겨우살이덩굴 in Korean) is a species of honeysuckle native to eastern Asia including China, Japan and Korea. It is a twining vine able to climb up to 10 metres (33 ft) high or more in trees, with opposite, simple oval leaves 3–8 centimetres (1.2–3.1 in) long and 2–3 centimetres (0.79–1.18 in) broad. The flowers are double-tongued, opening white and fading to yellow, and sweetly vanilla scented. The fruit is a black spherical berry 3–4 millimetres (0.12–0.16 in) diameter containing a few seeds.
It is an invasive species in a number of countries.
Cultivation, management and uses
This species is often sold by American nurseries as the cultivar 'Hall's Prolific' (Lonicera japonica var. halliana). It is an effective groundcover, and has pleasant, strong-smelling flowers. It can be cultivated by seed, cuttings, or layering. In addition, it will spread itself via shoots if given enough space to grow.
In both its native and introduced range, Japanese honeysuckle can be a significant source of food for deer, rabbits, hummingbirds and other wildlife.
Japanese honeysuckle has become naturalized in Argentina, Australia, Brazil, Mexico, New Zealand and much of the US, including Hawaii, as well as a number of Pacific and Caribbean islands.
Japanese honeysuckle is classified as a noxious weed in Texas, Illinois, and Virginia, and is banned in New Hampshire. It grows extremely rapidly in parts of America such as southwestern Ohio and is virtually impossible to control in naturalized woodland edge zones due to its rapid spread via tiny fruit seeds. It forms a tall dense woody shrub layer that aggressively displaces native plants. The succession cycle of a forest is not all that different than a human life span-70-100 years. Accordingly, it is the aggressive displacement that poses a long term threat to future generations of native forests.It is also very difficult to manage in semi-wild areas, such as in large rural yards.
Privacy and harborage
In densely populated urban settings, its quick dense growth, drought tolerance, disease immunity, early leafing and late leaf loss make it appreciated as a privacy screen. It is unlikely that the general public could be discouraged from valuing these benefits in spite of it being an invasive species. As well, in such urban or suburban settings, the effect on development of next-generation hardwoods is less than in an open forest of any acreage. In urban environments, it is also valued by laypeople as wildlife habitat. While Japanese honeysuckle is undoubtedly better for flora and fauna than no habitat, there is no evidence that it is better than native habitat and empirical reasoning would suggest that it is inherently not as a result of its well documented interference with normal succession cycles-especially of flora (plants).
It can be controlled to some degree via labor-intensive methods such as cutting or burning the plant to root level and repeating at two-week intervals until nutrient reserves in the roots are depleted. It can also be controlled through annual applications of glyphosate, or through grubbing if high labor and soil destruction are not of concern. Cutting the honeysuckle to within 5–10 cm of the ground and then applying glyphosate has proven to be more effective, provided that the mixture is rather concentrated (20–25%) and is applied immediately after making the cut.
In urban environments of Southwest Ohio where deer population is high, some level of longer-term management has been observed by cutting the honeysuckle to within 18-24" of the ground. Grazing deer substantially slow down regrowth. Once the canopy from a stand of honeysuckle or that of an individual plant exceeds the grazing height of deer, this control method is ineffective. It should be noted that as recently as the late 90s, Japanese honeysuckle was not considered to be part of a deers diet, but by 2010 urban SW Ohio deer can be observed grazing on it with enthusiasm. Especially freshly cut honeysuckle stocks.
While manual removal is impractical on a large scale basis, mechanized removal using grinding heads on track loaders and particularly on track excavators is worth considering. The arm reach of 10-30'feet from a single position of a track excavator allows a much higher ratio of cleared area to disturbed ground when compared to use of a grinding head on a track loader. The ratio of ground disturbance between using grinding head on track loader verse excavator could be as high as 1:10. Some of the concerns about use of such large equipment also removing developing native species is likely to be further limited by use of a track loader due to its much more precise method of movement. In this regard, selection of an operator who is familiar with native species and has a good understanding of the holistic objective is likely to do far less damage to desirable natives than an operator who sees the job only as a selective land clearing initiative. Further and lastly, the track excavator compared to the track loader has the ability to reach into swales and onto embankments without physically entering the slope.
Lonicera japonica contains methyl caffeate, 3,4-di-O-caffeoylquinic acid, methyl 3,4-di-O-caffeoylquinate, protocatechuic acid, methyl chlorogenic acid and luteolin. These compounds have an inhibitory effect on human platelet aggregation that may explain the possible role of Japanese honeysuckle in maintaining vascular homeostasis. The two biflavonoids, 3′-O-methyl loniflavone and loniflavone along with luteolin and chrysin can be isolated from the leaves. Other phenolic compounds present in the plant are hyperoside, chlorogenic acid and caffeic acid.
Traditional Chinese medicine
In traditional Chinese medicine, Lonicera japonica is called rěn dōng téng (Chinese: 忍冬藤; literally "winter enduring vine") or jīn yín huā (Chinese: 金銀花; literally "gold silver flower"). Alternative Chinese names include er hua and shuang hua. In Korean, it is called geumeunhwa. The dried leaves and flowers (Flos Lonicerae Japonicae) are employed in traditional Chinese medicine, being used to treat fever, headache, cough, thirst and sore throat.
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|Wikimedia Commons has media related to Lonicera japonica.|
- Plants For A Future: Lonicera japonica
- Species Profile- Japanese Honeysuckle (Lonicera japonica), National Invasive Species Information Center, United States National Agricultural Library. Lists general information and resources for Japanese Honeysuckle.