Lonicera japonica - Thunb.
Japanese Honeysuckle
Other Common Names: Japanese honeysuckle
Taxonomic Status: Accepted
Related ITIS Name(s): Lonicera japonica Thunb. (TSN 35283)
Unique Identifier: ELEMENT_GLOBAL.2.129271
Element Code: PDCPR030G0
Informal Taxonomy: Plants, Vascular - Flowering Plants - Honeysuckle Family
 
Kingdom Phylum Class Order Family Genus
Plantae Anthophyta Dicotyledoneae Dipsacales Caprifoliaceae Lonicera
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Concept Reference
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Concept Reference: Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Concept Reference Code: B94KAR01HQUS
Name Used in Concept Reference: Lonicera japonica
Conservation Status
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NatureServe Status

Global Status: GNR
Global Status Last Reviewed: 22Mar1994
Global Status Last Changed: 22Mar1994
Rounded Global Status: GNR - Not Yet Ranked
Nation: United States
National Status: NNA
Nation: Canada
National Status: NNA (13Oct2016)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (SNA), Arizona (SNA), Arkansas (SNA), California (SNA), Connecticut (SNA), Delaware (SNA), District of Columbia (SNA), Florida (SNA), Georgia (SNR), Hawaii (SNA), Illinois (SNA), Indiana (SNA), Iowa (SNA), Kansas (SNA), Kentucky (SNA), Louisiana (SNA), Maine (SNA), Maryland (SNA), Massachusetts (SNR), Michigan (SNA), Mississippi (SNA), Missouri (SNA), Nebraska (SNA), Nevada (SNA), New Hampshire (SNA), New Jersey (SNA), New Mexico (SNA), New York (SNA), North Carolina (SNA), Ohio (SNA), Oklahoma (SNA), Pennsylvania (SNA), Rhode Island (SNA), South Carolina (SNA), Tennessee (SNA), Texas (SNA), Utah (SNA), Virginia (SNA), West Virginia (SNA), Wisconsin (SNA)
Canada Ontario (SNA)

Other Statuses

NatureServe Global Conservation Status Factors

Range Extent Comments: Lonicera japonica is native of the Nagasaki area of Japan and was introduced to the United States in 1806 for horticultural purposes (Leatherman 1955). Apparently, Japanese honeysuckle was slow to escape after its first introduction. It was not reported in Chapman's Flora of the Southern States (1884) or the Sixth Edition of Gray's Manual of Botany (1889), but by 1919 was distributed from the Gulf of Mexico to New York and Massachusetts (Andrews 1919). The present range extends from Massachusetts to northern Florida, west to Texas, Kansas and Missouri, and north to Indiana, Illinois and Michigan.

Other NatureServe Conservation Status Information

Distribution
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Global Range: Lonicera japonica is native of the Nagasaki area of Japan and was introduced to the United States in 1806 for horticultural purposes (Leatherman 1955). Apparently, Japanese honeysuckle was slow to escape after its first introduction. It was not reported in Chapman's Flora of the Southern States (1884) or the Sixth Edition of Gray's Manual of Botany (1889), but by 1919 was distributed from the Gulf of Mexico to New York and Massachusetts (Andrews 1919). The present range extends from Massachusetts to northern Florida, west to Texas, Kansas and Missouri, and north to Indiana, Illinois and Michigan.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The distribution shown may be incomplete, particularly for some rapidly spreading exotic species.

U.S. & Canada State/Province Distribution
United States ALexotic, ARexotic, AZexotic, CAexotic, CTexotic, DCexotic, DEexotic, FLexotic, GA, HIexotic, IAexotic, ILexotic, INexotic, KSexotic, KYexotic, LAexotic, MA, MDexotic, MEexotic, MIexotic, MOexotic, MSexotic, NCexotic, NEexotic, NHexotic, NJexotic, NMexotic, NVexotic, NYexotic, OHexotic, OKexotic, PAexotic, RIexotic, SCexotic, TNexotic, TXexotic, UTexotic, VAexotic, WIexotic, WVexotic
Canada ONexotic

Range Map
No map available.

Ecology & Life History
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Basic Description: Japanese honeysuckle is a perennial, trailing or climbing woody vine.
Technical Description: Perennial, trailing or climbing woody vine with opposite, simple, pubescent leaves. In the south of the range the leaves are evergreen (Blair et al. 1983, Fernald 1950, Radford et al. 1964). Farther north leaves are semi-evergreen, i.e. fall off in midwinter (Schwegman pers. comm. 1987, Slezak 1976, Strausbaugh and Core 1978). Leaf shape varies from ovate and entire in mature leaves to lobed in young leaves. The fragrant white to yellow flowers are born in pairs on axillary peduncles. The fused corolla is 3-4 cm long with a pubescent tube. The inconspicuous berries are small, black and sessile, and contain 2-3 seeds in a mucilaginous pulp. The brown seeds are ovate to oblong, 2-3 mm long, with a flat to concave inner face and three ridges on the back (Fernald 1950, USDA 1971).
Diagnostic Characteristics: Lonicera japonica is distinguished from native twining honeysuckles by the fact that members of each pair of its leaves are distinct, whereas at least some of the opposite leaves of native twining species are united (Fernald 1950).
Reproduction Comments: Japanese honeysuckle produces long twining vegetative runners. Wherever they come in contact with the soil, runners can produce roots at the nodes, producing dense mats of plants; once runners from a single parent plant have established roots, they will resprout as separate individual plants if their aboveground parts are severed. It blooms most prolifically in sunny situations where the opportunity for vegetative proliferation is restricted (Andrews 1919). The inconspicuous black berries each contain three seeds (USDA 1971), which are dispersed by birds from light gap to light gap in forest (Martin et al. 1951).
Ecology Comments: The invasive ability of Japanese honeysuckle is the result of an interplay of four biological factors: the dispersal of its seeds by birds into light gaps of otherwise closed forests; its ability to propagate by vegetative runners; its particular method of twining, which restricts it to climbing vegetation with a small diameter but prevents its climbing the boles of mature trees; and its persistent evergreen leaves that permit photosynthesis during periods when the invaded vegetation is dormant.

Japanese honeysuckle blooms most prolifically in sunny situations where the opportunity for vegetative proliferation is restricted (Andrews 1919). Although the flower appears to be specialized, the plant is believed not to be dependent on any single insect because its blooming period extends from April to December in Georgia (Andrews 1919) and late May to October in Kentucky (Sather pers. obs.).

The inconspicuous black berries each contain three seeds (USDA 1971), which are dispersed by birds from light gap to light gap in forest (Martin et al. 1951). Seedlings are believed to photosynthesize soon after germination because their food content is low (Leatherman 1955). Despite the abundance of data relating to light requirements, most experimental studies have been conducted on cuttings, with no information on the light requirements for germination. Light requirements are probably not high because seedlings are known to become established in shaded understories. Little and Somes (1967) report that seedling growth is slow for the first two years of life. Because of their slow growth rate, new plants are unable to take advantage of canopy gaps. Once established, honeysuckle can persist at low light levels without noticeable growth and respond to increased light with more vigorous runner production.

In studies designed to measure the effect of shading on forage production in Texas, Blair et al. (1983) grew honeysuckle under light-intensities of 92%, 55%, and 0% of full sunlight. Although shade did not affect the timing of phenological events, there was a significant inverse relationship between leaf dry matter and light intensity at all levels of shading. In the deepest shade, new leaders were formed but died back.

Leatherman (1955) found that about half of her experimental cuttings survived at 10% of full sunlight and that at 25% full sunlight survival was good. There was no significant difference in the dry weight production between plants grown in 25% of full sunlight and those grown in full sunlight (Leatherman 1955).

Slezak (1976) divided honeysuckle-infested plots into density and vigor classes and found that vigor (measured by the number of vegetative runners) was adversely affected by shading of less than 3% of full sunlight, but density was unaffected. In experimental studies at Theodore Roosevelt Island National Park, Thomas (1980b) demonstrated that Japanese honeysuckle produced good growth at 47% of full sun and found from winter light measurements that all closed forest in the park had light levels between 49% and 86% of full sun during the winter months. Japanese honeysuckle is thus well adapted to persist in deciduous forests at low summer light intensities and put on growth when canopy gaps occur or at winter light levels.

Japanese honeysuckle has a long photosynthetic season. In the south, the plant is evergreen. In Illinois leaves fall when winter temperatures reach around 17 centigrades (Schwegman pers. comm. 1987). In areas where it is facultatively deciduous, it is one of the first plants to leaf in the spring. In New Jersey, leaf production begins when soil temperatures are between 1 and 9 centigrades (Leatherman 1955). In Illinois, Japanese honeysuckle produces leaves with the spring ephemerals and retains its leaves through November, allowing at least three months for photosynthesis in otherwise shaded deciduous forests (Schwegman pers. comm. 1987).

Thomas (1980b) calculated that in the Washington, D.C. area there are an average of 52 days a year between first and last frost when temperature and light conditions in closed canopy forests are adequate for honeysuckle photosynthesis. The combination of honeysuckle's ability to photosynthesize at winter temperatures and light levels and its ability to persist under summer shade appear to be the major factors contributing to its destructiveness. In areas where winter temperatures fall too low for the late season photosynthesis to occur, the species is less of a problem.

Japanese honeysuckle produces long twining vegetative runners. Little (1961) found that the combined length of lateral and sublateral runners from one sprout in one year reached 15 meters. In well-lit areas, Slezak (1976) found that 7% of sampled plots contained over 50% plants with seven or more runners over 60 cm in length. These runners serve a dual function. Wherever they come in contact with the soil, runners can produce roots at the nodes, producing dense mats of plants. In addition to their ability to root, the runners create new habitat by their twining habit. Unlike Virginia creeper, which climbs its host by holdfast, or grapevine, which possesses tendrils, honeysuckle climbs by twining around its host. This twining habit limits the diameter of accessible hosts, which may nonetheless be as great as 15 centimeters (Andrews 1919). Honeysuckle is unable to climb boles of mature trees although it uses other lianas to reach the canopy where they are available (Andrews 1919).

The root system of mature Japanese honeysuckle plants has been reported to reach depths as great as a meter and horizontal lengths up to 3 meters (Leatherman 1955). Wherever aboveground runners contact the ground they will root. Once runners from a single parent plant have established roots, they will resprout as separate individual plants if their aboveground parts are severed. Little and Somes (1967) report that it took only two years for honeysuckle to reach pre-treatment densities from root sprouts after a variety of herbicide applications.

Habitat Comments: Lonicera japonica is generally associated with disturbance and has spread to old fields, roadsides, fence rows, prairies, sand barrens and forest openings. In Pennsylvania, it is a major component of the third stage of succession in old fields, increasing after fields have been abandoned for four years (Keever 1979). Light appears to be the major limiting factor (Andrews 1919, Leatherman 1955, Thomas 1974), but recent studies suggest that Japanese honeysuckle can invade established woodlands when natural processes such as storms or Dutch elm disease create canopy openings (Thomas 1974, Slezak 1976). Invasion is particularly effective in moist woodlands and floodplain forests (Andrew 1919, Snyder pers. comm., Wistendahl 1958). Slezak (1976) found that in poorly drained areas the frequency of Japanese honeysuckle decreased with increasing canopy closure and understory closure had no significant effect. In well-drained areas, however, the frequency of Japanese honeysuckle was inversely correlated with closure of the subcanopy, but canopy coverage was not correlated with honeysuckle frequency (Slezak 1976). Japanese honeysuckle is one of the few species that can withstand pollution from heavy metals and SO2 (Caiazza and Quinn 1980).

Infestations have reached pest proportions in areas with annual precipitation of at least 100 cm and mean January temperatures of at least -1 C and freezing January night temperatures at least 5% of the nights (Leatherman 1955).

No discussion of the habitat of Japanese honeysuckle would be complete without mentioning that Lonicera japonica is still being propagated and promoted for use as a groundcover in areas where it has not reached pest proportions.

Economic Attributes Not yet assessed
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Management Summary Not yet assessed
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Population/Occurrence Delineation Not yet assessed
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Population/Occurrence Viability
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U.S. Invasive Species Impact Rank (I-Rank)
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Disclaimer: While I-Rank information is available over NatureServe Explorer, NatureServe is not actively developing or maintaining these data. Species with I-RANKs do not represent a random sample of species exotic in the United States; available assessments may be biased toward those species with higher-than-average impact.

I-Rank: High/Medium
Rounded I-Rank: High
I-Rank Reasons Summary: Lonicera japonica can have extremely negative consequences for forest communities and forest structure. Few effective control methods known.
Subrank I - Ecological Impact: Medium
Subrank II - Current Distribution/Abundance: High
Subrank III - Trend in Distribution/Abundance: High/Medium
Subrank IV - Management Difficulty: High/Medium
I-Rank Review Date: 18May2004
Evaluator: Fellows, M.
Native anywhere in the U.S?
Native Range: East Asia, including Japan and Korea (Nuzzo 1997, Weber 2003).

Download "An Invasive Species Assessment Protocol: Evaluating Non-Native Plants for their Impact on Biodiversity". (PDF, 1.03MB)
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Screening Questions

S-1. Established outside cultivation as a non-native? YES
Comments: (Kartesz 1999).

S-2. Present in conservation areas or other native species habitat? Yes
Comments: Reported as an important pest from mid-atlantic natural areas (Langeland and Burks 1998; Swearingen et al. 2002) and the mid-west (Nuzzo 1997).

Subrank I - Ecological Impact: Medium

1. Impact on Ecosystem Processes and System-wide Parameters:Low significance/Insignificant
Comments: Not reported to have ecosystem-level effects, therefore inferred to be low or insignificant.

2. Impact on Ecological Community Structure:High significance
Comments: Changes forest structure, topples trees and shrubs due to weight alone, forms dense blanket that suppresses understory shrubs and herbs, results in a simplified increasingly open understory (Nuzzo 1997). It can disrupt understory structure in mature fores and plant succession in once-forested areas by overtopping and smothering young trees, preventing their recruitment to the overstory (Langeland and Burks 1998). Shades out herbaceous species (Lindblom, The Nature Conservancy, pers. comm.). The root system alone has been recorded as 3m across and 1m deep (Nuzzo 1997).

3. Impact on Ecological Community Composition:High significance
Comments: Outcompetes and eliminates native flora by strong below-ground competition and having a high photosynthesis rate year-round because of evergreen leaves (Nuzzo 1997; Langeland and Burks 1998). May inhibit spring ephermerals from completing life cycle because of dense shade (Nuzzo 1997). Can kill adult trees and prevent establishment of seedlings (Nuzzo 1997).

4. Impact on Individual Native Plant or Animal Species:Moderate significance
Comments: Lonicera japonica has been linked to a decline or alteration in native songbird populations and an overabundance of white-tailed deer due to good winter foliage (Nuzzo 1997). Eliminates portions of forest structure that are important to birds (Langeland and Burks 1998). Enters steepheads, threatening state-listed species such as Xanthorhiza simplisissima (Burks, Florida Department of Environmental Protection, pers. comm.).

5. Conservation Significance of the Communities and Native Species Threatened:Moderate significance
Comments: Can invaded rare habitats like rocky glades (Merriam, The Nature Conservancy, pers. comm.). Threatens Hawaiian forests (Flynn and Lorence, pers. comm.).

Subrank II. Current Distribution and Abundance: High

6. Current Range Size in Nation:High significance
Comments: 39 states, East Coast, Southwest, Hawaii (Kartesz 1999).

7. Proportion of Current Range Where the Species is Negatively Impacting Biodiversity:High significance
Comments: FL (Langland and Burks 1998), NC, occupying c. 26% of edge habitat (Merriam 2003). A severe threat in southeastern and eastern states (Nuzzo 1997).

8. Proportion of Nation's Biogeographic Units Invaded:High/Moderate significance
Comments: Present in about half of TNC ecoregions (Kartesz 1999; TNC 2001; Morse, pers. comm.)

9. Diversity of Habitats or Ecological Systems Invaded in Nation:Moderate significance
Comments: Occurs most densely in open woodlands and prairies, but also invades mature forests (Langeland and Burks 1998), invades floodplains in eastern North America (Nuzzo 1997), common in dry-mesic to wet-mesic upland forest, floodplain forest, and southern pine stands (Randall, pers. comm.).

Subrank III. Trend in Distribution and Abundance: High/Medium

10. Current Trend in Total Range within Nation:Moderate significance
Comments: First record of sale occurred in 1823, since then it has naturalized in regions having greater than 100 cm annual rainfall and average dauly January temperature above 0 degrees C (Merriam 2003) - likely to already occur in all habitats in US, however, this species thrives on habitat fragmentation, and it will expand to new edge habitats as they are made. The species is also spreading slowly northward (Nuzzo 1997). It has also recently escaped cultivation in HI and CA (Nuzzo 1997).

11. Proportion of Potential Range Currently Occupied:Low significance/Insignificant
Comments: One of the most common vine species in the southeast (Langeland and Burks 1998). First record of sale occurred in 1823, since then it has naturalized in regions having greater than 100 cm annual rainfall and average dauly January temperature above 0 degrees C (Merriam 2003).

12. Long-distance Dispersal Potential within Nation:High significance
Comments: Still planted along highways and in gardens (Nuzzo 1997); ornamental horticulture in the Southeast and sometimes promoted as deer forage. Fruits eaten by deer, rabbits, turkeys, quail, with seed dispersed primarily by birds (Nuzzo 1997; Langeland and Burks 1998; Weber 2003). In 1899, Lonicera japonica was described as the most widely planted honeysuckle in the U.S. (Nuzzo 1997).

13. Local Range Expansion or Change in Abundance:High/Low significance
Comments: Spreads quickly vegetatively and by seed (Nuzzo 1997).

14. Inherent Ability to Invade Conservation Areas and Other Native Species Habitats:Moderate significance
Comments: It is definitely an edge invader (Randall, pers. comm.). However, it will also spread and persist under a canopy, just a bit slower than in full sun (Lindblom, The Nature Conservancy, pers. comm.). Thrives in tree gaps created by natural or artificial disturbance and persisting in partially shaded areas (Langeland and Burks 1998).

15. Similar Habitats Invaded Elsewhere:Low significance
Comments: Afghanistan, Argentina, Australia, Brazil, Chile, England, New Zealand (Nuzzo 1997; Weber 2003; Burks, Florida Department of Environmental Protection, pers. comm.). Also non-native and established in central Europe (Weber 2003). All invaded habitats are similar to already invaded habitats in U.S. (Weber 2003).

16. Reproductive Characteristics:High significance
Comments: Reproduces readily both vegetatively and by seed, has quickly spreading rhizomes that may root at nodes, aboveground runners, and resprouts readily when cut, grazed or burned (Nuzzo 1997).

Subrank IV. General Management Difficulty: High/Medium

17. General Management Difficulty:High significance
Comments: Removing above-ground stems by cutting pulling or burning will temporarily weaken, but not kill this species as it will resprout from subterranean buds and roots, and from cut branchlets once established (Nuzzo 1997). Hand pull when shrubs are small, but remove all rooting stems; a foliar herbicidal application after the first frost will effectively control established plants (Nuzzo 1997; Weber 2003).

18. Minimum Time Commitment:Medium/Low significance
Comments: Mowing twice a year can slow vegetative spread, however due to recurrent resprouting, stem density may increase (Swearingen et al. 2002). Extremely difficult to remove after it's been established (Nuzzo 1997).

19. Impacts of Management on Native Species:Medium/Low significance
Comments: In Florida, it is extremely difficult to control without nontarget damage to natives (Burks, Florida Department of Environmental Protection, pers. comm.). However, applying herbicide after first frost or during winter months when it is one of the few evergreen shrubs, decreases nontarget damage (Nuzzo 1997).

20. Accessibility of Invaded Areas:High/Low significance
Comments: Present in many reatively remote areas in the eastern US (Morse, pers. comm.).
Authors/Contributors
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NatureServe Conservation Status Factors Edition Date: 09Apr1987
NatureServe Conservation Status Factors Author: N. SATHER
Element Ecology & Life History Edition Date: 09Apr1987

Botanical data developed by NatureServe and its network of natural heritage programs (see Local Programs), The North Carolina Botanical Garden, and other contributors and cooperators (see Sources).

References
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  • Larson, B. M. H., Catling, P. M. and Waldron, G. E. 2007. The biology of Canadian weeds. 135. Lonicera japonica Thunb. Canadian Journal of Plant Science 87: 423?438.


  • Andrews, E. F. 1919. The Japanese honeysuckle in the eastern United States. Torreya 19: 37-43.

  • Blair, R. M., R. Alcaniz, and A. Harrell. 1983. Shade intensity influences the nutrient quality and digestibility of southern deer browse leaves. Journ. Range Mang. 36: 257-264.

  • Caiazza, N. A., and J. A. Quinn. 1980. Leaf morphology in Arenaria patula and Lonicera japonica along a pollution gradient. Bull. Torr. Bot. Club 107: 9-18.

  • Catling, P.M., B.M.H. Larson, and G. Waldron. 2006. Japanese Honeysuckle, an addition to the prioritized list of the invasive alien plants of natural habitats in Canada. Botanical Electronic News (BEN) No. 357. (http://www.ou.edu/cas/botany-micro/ben/ben357.html)

  • Deam, C. C. 1940. Flora of Indiana. Division of Forestry, Dept. of Conservation, Indianapolis, Indiana. 1236 pp.

  • Fernald, M. L. 1950. Gray's manual of botany. 8th edition. Corrected printing (1970). D. Van Nostrand Company, New York. 1632 pp.

  • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.

  • Kartesz, J.T. 1996. Species distribution data at state and province level for vascular plant taxa of the United States, Canada, and Greenland (accepted records), from unpublished data files at the North Carolina Botanical Garden, December, 1996.

  • Kartesz, J.T. 1999. A synonymized checklist and atlas with biological attributes for the vascular flora of the United States, Canada, and Greenland. First edition. In: Kartesz, J.T., and C.A. Meacham. Synthesis of the North American Flora, Version 1.0. North Carolina Botanical Garden, Chapel Hill, N.C.

  • Keever, C. 1979. Mechanisms of plant succession on old fields of Lancaster County, Pennsylvania. Bull Torrey Bot. Club 106: 299-308.

  • Langeland, K.A. and K.C. Burks. 1998. Identification and Biology of Non-Native Plants in Florida's Natural Areas. University of Florida. 165 pp. [http://aquat1.ifas.ufl.edu/identif.html]

  • Leatherman, A. D. 1955. Ecological life-history of Lonicera japonica thunb. Ph.D. thesis, University of Tennessee. 97 pp.

  • Little, S. 1961. Recent tests in controlling Japanese honeysuckle. The Hormolog 3(1): 8-10.

  • Little, S., and H. A. Somes. 1967. Results of herbicide trials to control Japanese honeysuckle. U.S. Forest Service, Northeast Forest Exp. Sta. Res. Note 62: 18.

  • Little, S., and H. A. Somes. 1968. Herbicide treatments of Japanese honeysuckle for releasing desirable reproduction or for site preparation. USDA, Forest Service. Northeastern Forest Exper. Sta., Research Note NE-83.

  • Martin, A.C., H.S. Zim, and A.L. Nelson. 1951. American wildlife and plants: A guide to wildlife food habits. Dover Publications, Inc., New York, NY. 500 pp.

  • Merriam, R. W. 2003. The abundance, distribution and edge associations of six non-indigenous, harmful plants across North Carolina. Journal of the Torrey Botanical Society 130(4):282-291.

  • Nuzzo, V. 1997. Element stewardship abstract for Lonicera japonica - Japanese honeysuckle. The Nature Conservancy. Arlington, VA.

  • Oldham, M.J., W.G. Stewart, and D. McLeod. 1993. Additions to "A Guide to the Flora of Elgin County, Ontario" for 1992.  The Cardinal No. 151: 18-20.

  • Radford, A.E., H.E. Ahles, and C.R. Bell. 1968. Manual of the vascular flora of the Carolinas. Univ. North Carolina Press, Chapel Hill, NC. 1183 pp.

  • Slezak, W. F. 1976. Lonicera japonica Thunb., an aggressive introduced species in a mature forest ecosystem. M. S. Thesis, Rutgers University, New Brunswick, New Jersey. 81 pp.

  • Soper, J.H. and M.L. Heimburger. 1982. Shrubs of Ontario. Royal Ontario Museum, Toronto. 495 pp.

  • Strausbaugh, P.D., and E.L. Core. 1978. Flora of West Virginia. Seneca Books, Inc., Grantsville, WV. 1079 pp.

  • Swearingen, J., K. Reshetiloff, B. Slattery, and S. Zwicker. 2002. Plant Invaders of Mid-Atlantic Natural Areas. National Park Service and U.S. Fish & Wildlife Service, 82 pp.

  • Swink, F., and G. Wilhelm. 1994. Plants of the Chicago Region. Morton Arboretum. Lisle, Illinois.

  • The Nature Conservancy. 2001. Map: TNC Ecoregions of the United States. Modification of Bailey Ecoregions. Online . Accessed May 2003.

  • Thomas, L. K. 1980a. The impact of three exotic plant species on a Potomac island. National Park Service scientific monograph series; No. 13. U.S. Department of the Interior, Washington, D.C. 179 pp.

  • Thomas, L. K., Jr. 1980b. Winter growth of Japanese honeysuckle (Lonicera japonica Thunb.) on Theodore Roosevelt Island, District of Columbia. In Proc. 2nd Conf. on Sci. Res. in the National Parks. Vol. 8: 408-418.

  • United States Department of Agriculture, Agricultural Research Services. 1971. Common Weeds of the United States. New York: Dover Publications, Inc.

  • Weber, E. 2003. Invasive plant species of the world: a reference guide to environmental weeds. CABI Publishing, Cambridge, Massachusetts. 548 pp.

  • Wistendahl, W. A. 1958. The flood plain of the Raritan River, New Jersey. Ecol. Mon. 28: 143-151.

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