Lonicera japonica

Biological Category

Plants

Species Type

Vine

NY Legal Status

Prohibited

NY Invasiveness Rank

Very High

LHPrism Status

Tier 4 - Widespread

Key Characteristics

Leaf

Leaves are oval and have a smooth margin. They occur in pairs opposite each other along the stem, similar to airplane propellers.

Flower

Flowers are tubular and cluster in pairs along the stem. The petals are white to pale yellow and asymmetric (two lipped) with one having 4 lobes and the other unlobed.

Fruit

Spherical black berries are 3-4mm in size.

Growth Form

Perennial woody, twining vine with thin stems, growing up to 10 m. in height but often forming mats along the forest floor.

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Description

Japanese honeysuckle is a member of the Honeysuckle family (Caprifoliaceae). It is a perennial, woody vine that can grow to be 30 feet long. Japanese honeysuckle is most easily identified in early summer when fragrant clusters of gold to yellow to creamy white trumpets bloom (5). These flowers are generally borne in pairs along the leaf axils. Leaves are alternately arranged, highly variable in shape, dark green and generally glossy on the surface. Leaf margins vary from coarsely serrate to deeply lobed and serrate. Japanese honeysuckle’s fruit is a small dark purple to black berry. (5)

Introduction History

Introduced via the horticultural trade in the early 1800s, Japanese honeysuckle was coveted by gardeners for its fragrant flowers and rampant, wild growth habit. (3). Land managers also intentionally planted the species for its ability to spread rapidly, curbing erosion at vulnerable sites such as roadside embankments (6).

Ecology and Habitat

Japanese honeysuckle is tolerant of a variety of soil types in full sun to shade. Although the species is strongly associated with anthropogenic disturbance, this invasive is capable of establishing under a closed canopy. In the Hudson Valley, Japanese honeysuckle is commonly seen at lower elevations, in early successional habitats and waste places such as roadsides, shrub thickets, disturbed woodlands and woodland edges.

Reproduction and Phenology

Although Japanese honeysuckle appears to reproduce well in North America, each fruit contains only 2-3 seeds and germination rates are not typically high. (6) More problematic is the species’ aggressive vegetative growth, and ability to spread locally very quickly via runners. (6) Vectors include birds and small mammals. (4)

Impacts of this species

Japanese honeysuckle is an aggressive, woody vine that can cover understory shrubs and ascend into the canopy— although this is more commonly seen further south. As a ground cover, this species is capable of smothering seedling trees and other herbaceous plants, preventing germination and displacing native vegetation. The homogenous understory Japanese honeysuckle forms can drastically alter forest bird communities. (6)

Management Methods

Biological Control
There is currently no single optimal biological control agent in use against this species. (4)

Manual or Mechanical Control
Pulling / Digging Up: Pulling by hand is an effective method of control for seedlings and small plants as long as all the root is extracted from the soil. For larger plants, this is an inadvisable technique as root fragmentation can encourage re-sprouting. (5)

Mowing: While mowing will limit the length of Japanese honeysuckle’s vines, it will encourage further sprouting, increasing the total number of runners present. (7)

Girdling: Not applicable

Prescribed Fire: Consistent, low-grade wildfires appear capable of excluding Japanese honeysuckle from the target habitat. However, sporadic fires will not kill the vine, which sprouts readily from roots or stems buried in leaf litter or soil (4)

Prescribed Grazing: Not applicable

Soil Tilling: Not advisable. Tilling may fragment roots and encourage re-sprouting.

Mulching: Not applicable

Solarization: Not applicable

Hot Foam Spray: Not applicable

Chemical Control
The pesticide application rates and usage herein are recommendations based on research and interviews with land managers. When considering the use of pesticides, it is your responsibility to fully understand the laws, regulations and best practices required to apply pesticides in a responsible manner. At times, the pest you seek to treat may not be on a pesticide label, requiring a 2ee exemption from NYSDEC. Always thoroughly read the label of any pesticide and consult the NYSDEC or a licensed pesticide applicator with questions.

Foliar Spray: A 2-3% solution of glyphosate is effective at managing Japanese honeysuckle, although a repeat application will likely be necessary. Infestations managed in this way should be revisited in 2-3 weeks to monitor for regrowth. Always read and follow all instructions on the herbicide label. (7)

Cut Stump: Not applicable

Basal Bark: No information available

Hack-And-Squirt

Stem Injection: Not applicable

Pre-Emergent Spray: Not applicable

Summary of Best Managment Practices

General management overview and recommendation
As with any other invasive infestation complex, large stands of Japanese honeysuckle are best managed via a combination of mechanical and chemical means. Spring wildfires or sequential mowing followed by foliar spray of the vegetation that re-sprouts will likely give the most complete control. Managed infestations should be monitored for at least three years to ensure exhaustion of the short-lived seed bank (8). Any new seedlings can be hand pulled. (7)

Post treatment monitoring
Any infestations managed by chemical means must be revisited in 2-3 weeks to check for treatment efficacy. Although the species does not appear capable of forming long-term seed banks, treated populations should be revisited for at least three years to ensure no new seedlings have germinated (8).

Disposal Methods
Waste material can be crushed, chipped, burned or composted so long as management was completed prior to seed set. Any fruit must be bagged and disposed of, and any roots thoroughly crushed or dried.

Additional Information

REFERENCES

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