Lonicera japonica

Lonicera japonica, known as Japanese honeysuckle<ref name=BSBI07>Template:BSBI 2007</ref> and golden-and-silver honeysuckle,<ref>Template:Cite book</ref> is a species of honeysuckle native to East Asia, including many parts of China. It is often grown as an ornamental plant, but has become an invasive species in a number of countries. It is used in traditional Chinese medicine.

Description

Lonicera japonica is a twining vine<ref>Template:Cite book</ref> able to climb up to Template:Convert high or more in trees, with opposite, simple oval leaves Template:Convert long and Template:Convert broad. When its stems are young, they are slightly red in color and may be fuzzy. Older stems are brown with peeling bark, and are often hollow on the inside.<ref name=":02">Template:Cite web</ref>

The flowers are double-tongued, opening white and fading to yellow, and sweetly vanilla scented. The fruit, which is produced in fall,<ref name=":02"/> is a black spherical berry Template:Convert diameter containing a few seeds.<ref>Template:Cite web</ref>

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Chemistry

Lonicera japonica contains methyl caffeate, 3,4-di-O-caffeoylquinic acid, methyl 3,4-di-O-caffeoylquinate, protocatechuic acid, methyl chlorogenic acid, and luteolin. The two biflavonoids, 3′-O-methyl loniflavone and loniflavone, along with luteolin and chrysin, can be isolated from the leaves.<ref>Template:Cite journal</ref> Other phenolic compounds present in the plant are hyperoside, chlorogenic acid, and caffeic acid.<ref>Template:Cite journal</ref> The two secoiridoid glycosides, loniceracetalides A and B, can be isolated, together with 10 known iridoid glycosides, from the flower buds.<ref>Template:Cite journal</ref> The plant also contains the saponins loniceroside A and B<ref>Template:Cite journal</ref> and the anti-inflammatory loniceroside C.<ref>Template:Cite journal</ref>

Subspecies

There are three subspecies of Lonicera japonica:

Image	Subspecies	Description	Distribution
	Lonicera japonica var. chinensis Template:Small	Corolla purple outside, white inside. Usually diploid 2n=18	China (Anhui, 安徽省 in Chinese) around 800 meters<ref name=foc200022325>Template:EFloras</ref>
	Lonicera japonica var. japonica	Vigorous vine, Corolla white, later yellow-white. Usually diploid 2n=18	Grows on the edge of forest in China, Japan, and Korea<ref name=foc242330396>Template:EFloras</ref>
	Lonicera japonica var. miyagusukiana Template:Small	Tetraploid with chromosome number of 2n=36	Found in tops of exposed windy limestone cliffs in Ryukyus Islands, Japan<ref name="Denda Koja Yokota 2007 pp. 331–337">Template:Cite journal</ref>

Ecology

The flowers can also be a significant source of food for deer, rabbits, hummingbirds, and other wildlife.<ref>Forest Plants of the Southeast and Their Wildlife Uses, James H. Miller and Karl V. Miller, University of Georgia Press, Revised Ed. 2005, p.278</ref>

As an invasive species

Japanese honeysuckle has become naturalized in Argentina, Australia, Brazil, Mexico, New Zealand, and much of the United States, including Hawaii, as well as a number of Pacific and Caribbean islands. It is classified as a noxious weed in 46 states, Prohibited to be bought and sold in Connecticut, Illinois, Massachusetts, and Vermont, and banned in Indiana and New Hampshire.<ref>Template:Cite web</ref><ref>Template:Cite web</ref> It is on the New Hampshire invasive species list.<ref>Template:Cite web</ref>

Lonicera japonica was initially brought to the U.S. from Japan in the early 1800s as an ornamental plant. It is still deliberately planted in the U.S. for reasons such as erosion control or forage for deer, but has become invasive in many areas.<ref name=":02" /> It prefers to invade areas that have been disturbed, such as roadsides or floodplains. It will generally only invade forests when the canopy has been opened by logging or fallen trees, as it grows less vigorously in the shade.<ref>Template:Cite web</ref> Once it has invaded an area, Lonicera japonica grows rapidly and outcompetes native plants for sunlight and nutrients.<ref name=":02" /> It proliferates using both sexual and vegetative reproduction, producing seeds that are spread by animals and expanding locally via rhizomes.<ref name=":1">Template:Cite web</ref> Eventually, it will form a dense thicket which prevents other plant species from germinating in that area.<ref name=":02" /> Due to its suppression of germination in the understory, Lonicera japonica also prevents the regeneration of trees.<ref name=":2">Template:Cite web</ref>

Lonicera japonica's rapid growth allows it to outcompete other plants in the areas it invades.

Management of invasive Lonicera japonica has been achieved through a variety of means. Small patches can be removed by hand, or using simple digging tools,<ref name=":1" /> but all plant parts including roots and rhizomes must be removed to prevent resprouting.<ref name=":02" /> Larger patches can be removed through repeated mowing, but application of herbicide is also recommended to prevent regrowth.<ref name=":1" /> There has been some study of using controlled burns to remove L. japonica, but the underground portion of the plant is usually able to survive and resprout, limiting the effectiveness of this method.<ref name=":02" /> Browsing by herbivores may limit its growth, but is unlikely to fully eliminate it.<ref name=":2" />

Biological control

The EPA of New Zealand approved the release of Limenitis glorifica butterflies in 2013 as a biological control for Lonicera japonica. This butterfly is host specific for Japanese honeysuckle, but it may incidentally feed on other closely related plants, including Himalayan honeysuckle Leycesteria formosa.<ref>Template:Cite web</ref> Oberea shirahatai is a Japanese honeysuckle host-specific beetle that feeds on the stems and leaves of Japanese honeysuckle. It was released in New Zealand in 2018 as another L. japonica-specialist biological control.<ref>Template:Cite web</ref>

Cultivation

Even though it is a highly invasive and destructive plant,<ref>Template:Cite web</ref> this species is often sold by American nurseries as the cultivar 'Hall's Prolific' (Lonicera japonica var. halliana),Template:Citation needed and in the UK as the cultivar 'Halliana'. The cultivar is also known as Hall's Japanese honeysuckle.<ref>Template:Cite web</ref> It is an effective groundcover and has 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. The variety L. japonica var. repens<ref>Template:Cite web</ref> has gained the Royal Horticultural Society's Award of Garden Merit.<ref>Template:Cite web</ref>

Toxicity

All parts of the plant other than the flower nectar have the potential to be toxic.<ref>Template:Cite web</ref>

Uses

Japanese honeysuckle flowers are edible to humans and appreciated for their sweet-tasting nectar.Template:Citation needed

Herbal medicine

In traditional Chinese medicine,<ref name="Shang">Template:Cite journal</ref> Lonicera japonica is called rěn dōng téng (Template:WtTemplate:Wt);<ref name="Shang" /> literally "winter enduring vine") or jīn yín huā<ref name="Shang" /> (Template:Zh; literally "gold-silver flower", in reference to the presence of flowers of different age on the same plant as each flower change from white (silver) to yellow (gold)).Template:Citation needed Alternative Chinese names include er hua (二花) and shuang hua (雙花), meaning double-[color] flowers.<ref>Chinese Medical Herbology and Pharmacology, John and Tina Chen, Art of Medicine Press, 1st ed. 2001, p. 171</ref><ref>Template:Cite book</ref>