Photographers: James H. Miller & Ted Bodner Affiliation: Southern Weed Science Society Source: Bugwood.org Copyright: (CC BY 3.0)
Lonicera japonica is a twining vine with stems up to 4 inches in diameter. It can grow up to 18 feet or more in length and root depth is generally 6 to 12 inches for wet habitats and up to 40 inches in dry habitats. Roots can extend up to 8.5 feet laterally from the root crown. Overall the plant is an evergreen in the southern parts of its invasive range. Flowers are yellow to white and have a nice fragrance. Fruits are berries with 2-5 seeds per fruit.
This plant is on the Noxious Weed lists for 46 states and is prohibited for sale or import in CT, IL, MA, NH (though not reported there) and VT. Despite its relative affinity for open habitats, Japanese honeysuckle also has the ability to spread extensively within mature forest, persisting for many years in the understory. This plant directly impacts native plants by competing for sunlight and in turn blocking the sunlight with their dense canopy. Trees or shrubs they climb upon also can get pulled down by this plant once they’ve die. Since this plant is able to function as a climbing vine or a dense mat it allows it to be more adaptable than native vines such as the trumpet honeysuckle (Lonicera sempervirens). Even though this vine is used as cover and food by birds, insects and mammals alike, it outcompetes native honeysuckle and can overtake and understory changing the forest composition.
Lonicera japonica is pollinated by insects and hummingbirds; but it can also grow vegetatively. Flowering and seed production is more numerous when the plants are grown in an open area. In eastern Texas, open-grown plants started bearing seeds at 3 years compared to 5 years in shade-grown areas. Seed production declines after 6 years and they are dispersed by frugivorous birds and small mammals. Once established, colonies can spread rapidly and in the absence of stems to twine upon, they can form dense monospecific mats up to 5 feet deep.
Introduced to North America in the early 1800s and spread from New England to the Ohio Valley, in the 1940s it spread down south to the Atlantic and Gulf coastal plains. Afterwards it went to the Midwest in the 1980s and over to Texas all the way to California and Washington.
U.S. Habitat: Prefers open spaces but easily invades forest understory. Can be found in several types of habitats in the United Statesincluding fields, forests, wetlands, barrens, and all types of disturbed lands.
U.S. Present: AL, AR, AZ, CA, CT, DC, DE, FL, GA,HI, IL, IN, KS, KY, LA, MA, MD, ME, MI, MO, MS, NC, NE, NH, NJ, NM, NV, NY, OH, OK, PA, PR, RI, SC, TN, TX, UT, VA, WA, WI and WV
The native trumpet honeysuckle (Lonicera sempervirens) and the invasive Amur honeysuckle (Lonicera maakii) both resemble the Japanese honeysuckle because they are all in the Lonicera genus. Good alternatives to this invasive plant are false jasmine (Gelsemium sempervirens), trumpet creeper (Campsis radicans), crossvine (Bignonia capreolata), native wisteria (Wisteria frutescens), jackman clematis (Clematis jackmanii), and others.
Controlling Japanese honeysuckle may require determined and continual effort. Because it readily sprouts in response to stem damage, single treatments are unlikely to eradicate established plants. In areas where invasive Japanese honeysuckle suppresses populations of rare native plant species, control efforts require careful consideration, so the invasive plant is not stimulated to grow more and take over. No biological controls are known for this honeysuckle but combined mechanical and chemical strategies can provide some effectiveness for management. Mowing or cutting combined with herbicide treatment can work; but it usually requires several years of repeated application. Systemic herbicides such as glyphosate and triclopyr are effective even in foliar application.
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Williams, Peter A.; Timmins, Susan M. 1999. Biology and ecology of Japanese honeysuckle (Lonicera japonica) and its impacts in New Zealand. Science for Conservation: 99. Wellington, New Zealand: Department of Conservation. 21 p.