Japanese honeysuckle (Invasive Plants of Maryland)

Japanese honeysuckle

Lonicera japonica

Description and biology ⁸

Plant: perennial, deciduous to semi-evergreen twining vine; stems are pubescent and reddish brown to light brown.
Leaves: paired (opposite), ovate to oblong-ovate, about 1-3 in. long by ½-1½ in. wide, entire-margined except for young leaves which are often deeply toothed.
Flowers, fruits and seeds: flowers are bi-lobed, white turning yellow, highly fragrant and with nectar, produced in June; fruits are black, about ¼ in. diameter, paired, produced in the fall.
Spreads: by seed that is dispersed by birds.
Look-alikes: native trumpet honeysuckle which has red or yellow, long tubular flowers.

Ecological threat in the united states ⁹

In North America, Japanese honeysuckle has few natural enemies which allows it to spread widely and out-compete native plant species. Its evergreen to semi-evergreen nature gives it an added advantage over native species in many areas. Shrubs and young trees can be killed by girdling when vines twist tightly around stems and trunks, cutting off the flow of water through the plant. Dense growths of honeysuckle covering vegetation can gradually kill plants by blocking sunlight from reaching their leaves. Vigorous root competition also helps Japanese honeysuckle spread and displace neighboring native vegetation.

New york state invasive species information ¹⁰

Origin and Introduction: Lonicera tatarica is native to Central Asia and Southern Russia and is believed to have been introduced into North America for ornamental purposes as early as the 1750s. Lonicera japonica, – a native of China, Japan and Korea – was introduced for horticultural purposes in 1806 on Long Island; it was widely distributed as a garden plant through the early-1900s when it was finally recognized as a weed. Lonicera maackii, also native to China, Japan and Korea, was introduced as seeds to arboreta throughout the U.S. in the late-1800s to determine whether the plant would grow in North America. This species of honeysuckle was utilized as a soil stabilization and wildlife planning until the mid-1980s and is still available for sale on-line. Lonicera morrowii, a native of Japan, was imported to Massachusetts in the 1860s and was later released as an ornamental. All four species have escaped cultivation and are easily spread by birds.

Identification:Lonicera morrowii, Lonicera tatarica, and Lonicera maackii, are perennial shrubs; Lonicera japonica is a perennial woody vine (although its leaves can remain green throughout mild winters). The shrub forms range from 6 to 15 feet in height, while vines can reach 30 feet in length. The egg-shaped leaves range from 1 to 3 inches in length and are arranged oppositely along stems. Invasive honeysuckles begin flowering from May to June and bear small (less than 1 inch long), very fragrant tubular flowers ranging from creamy white through various shades of pink to crimson. Lonicera morrowii and Lonicera tatarica produce ¼ inch red berries from mid-summer through early-fall; Lonicera maackii’s dark-red berries don’t ripen until late-fall; Lonicera japonica produces dark-purple or black berries in the fall. Stems of all four are hollow.

Impacts:

All three species can form very dense populations that can outcompete and suppress the growth of native plant species. These dense stands suppress the growth of other native species. Lonicera maackii leafs out very early in spring, giving it a competitive advantage over native plants. Lonicera japonica leaves are semi-evergreen allowing the plant to grow longer into the winter and giving it a competitive advantage over native vegetation. It shades out understory growth preventing the success of native understory plants and tree seedlings. Its vigorous vine growth covers native trees; the weight of the vine growth can bring down weak trees. By decreasing light availability to the understory, these invasive honeysuckles can alter habitats by depleting soil moisture and nutrients. The invasive honeysuckle berries do not contain the amount of fat and nutrients present in native honeysuckle berries; eating large amounts of the less nutritious invasive berries rather than native berries can have negative impacts on migrating.

Prevention and Control:

Because these plants spread rapidly via birds eating seeds, control should be started in late-summer or early-fall before seeds are ready to be dispersed. In early stages of invasion, or in cases where populations are at low levels, hand removal of honeysuckle seedlings or young plants is a viable option when repeated annually. Systemic herbicides can be utilized in cases of heavy infestation. Specific state rules should be followed and the appropriate (low environment impact, legally labeled for control of these plants) herbicides should be used. For invasive honeysuckles growing in open habitats, prescribed burning may be an effective control alternative.

Prevention and control ¹¹

Small infestations can be controlled by hand removal of vines. Large infestations require mowing twice or more per year or treatment with systemic herbicides like those containing glyphosate or triclopyr. No biological controls are available.

Sources and Credits

(c) bbi2, some rights reserved (CC BY-NC), uploaded by bbi2
(c) Rolf Theodor Borlinghaus, some rights reserved (CC BY-NC), uploaded by Rolf Theodor Borlinghaus
(c) dcbioblitz, some rights reserved (CC BY-NC)
(c) Priyantha Wijesinghe, some rights reserved (CC BY-NC), uploaded by Priyantha Wijesinghe
(c) dottiew, some rights reserved (CC BY-NC)
(c) Carrie Seltzer, some rights reserved (CC BY-NC), uploaded by Carrie Seltzer
(c) Don Rideout, some rights reserved (CC BY-NC), uploaded by Don Rideout
(c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22734001
(c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22948687
(c) The New York Invasive Species Clearinghouse, Cornell University Cooperative Extension, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/23219499
(c) Unknown, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/22734002

More Info

iNat Map

Flower color	yellow

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