Japanese honeysuckle (Lonicera japanica) is an extremely vigorous perennial vine that is deciduous in northern climates but often evergreen in warmer areas. It is prized for its long bloom period and fragrant flowers that bloom all summer and into fall, but it is also sometimes despised because its "vigorous" growth habit all too easily strays over into invasiveness. In certain regions, this is a species you should not plant. Japanese honeysuckle is a climber that twines thickly around any vertical structure, whether it is a trellis or a tree. The vines bear fragrant white flowers, tinged with pink, that attract butterflies and hummingbirds from late spring into fall. The flowers gradually fade to yellow, and it is not uncommon to see white, pink, and yellow colors all at the same time. The flowers give way to black berries that are mildly poisonous to humans. The vine is often planted because it does well in shady locations and in dry soils.
- Botanical Name: Lonicera japonica
- Common Names: Japanese honeysuckle, golden-and-silver honeysuckle, Japanese honeysuckle weed
- Plant Type: Perennial flowering vine
- Mature Size: 15 to 30 feet in length, with a spread of 3 to 6 feet.
- Sun Exposure: Full sun to part shade
- Soil Type: Prefers average soil that is well drained
- Soil pH: 5.5 to 8
- Bloom Time: Late spring to fall
- Flower Color: White, maturing to yellow
- Hardiness Zones: 4 to 9
- Native Area: Eastern Asia including China, Japan, and Korea
How to Grow Japanese Honeysuckle
Although Japanese honeysuckle prefers moist, loamy soils, these ideal conditions can cause the plant to grow too vigorously. It does well in dry conditions, which can also help check its rampant growth. Plant it in full sun to part shade; shadier locations will both reduce the amount of flowering and also stunt the plant's growth somewhat.
Trained on a trellis, a single plant is normally used. When planted as a ground cover, use 2 or 3 plants for each square yard of ground. Ground cover plants should be sheared back with a lawn mower in later winter to control growth and remove any dead undergrowth.
This is an adaptable plant that does well in full sun to part shade, but a shadier location is sometimes preferred in order to keep its growth in check.
Japanese honeysuckle does well in any average soil, provided it is well drained. Dryer soils may limit the rampant growth habit of the vine.
For best growth, keep Japanese honeysuckle well watered (1 inch per week) and protect the soil with a layer of bark mulch. If the plant becomes too dry, leaves will turn brown and fall off, though the vine itself rarely dies. Withholding water may help keep the vine in check.
Temperature and Humidity
Japanese honeysuckle thrives in diverse conditions throughout its hardiness zone range. It is deciduous in colder climates; evergreen in warmer zones, but extremely vigorous wherever it grows.
The only feeding required is a layer of compost plus organic fertilizer in the spring. Withhold even this spring feeding if the vine becomes too vigorous.
Propagating Japanese Honeysuckle
This plant is rarely propagated deliberately due to its aggressive growth habit, but where desired, it is easily propagated by planting seeds from the berries, or by splitting off sections of its spreading rhizomatous roots.
Varieties of Japanese Honeysuckle
The variety of Japanese honeysuckle most often planted for landscape purposes is 'Halliana', commonly called Hall's honeysuckle. It is said to be less invasive than the native species; however, gardeners are strongly discouraged from planting any form of Japanese honeysuckle in many regions, especially the lower Midwest and Southeast.
Toxicity of Japanese Honeysuckle
Many species of honeysuckle are toxic to one degree or another, and this includes Japanese honeysuckle. This plant contains carotenoids in the berries and glycosides in the stems and vines. These are considered mildly toxic, and symptoms can include stomach pain, diarrhea, irregular heartbeat, and vomiting. But the effects are usually mild, and occur only when large quantities are ingested. You should not plant this vine where children are around, but the plant does attract butterflies and hummingbirds, and many birds enjoy eating the berries.
Major pruning should be done in the early winter after the flowers have dropped off. Pruning usually aims at shortening the plant and keeping its size in check. Plants grown as ground cover should be mowed down in the early spring with a mower set at maximum height.
There are many other forms of honeysuckle that offer some of the same benefits but without the dangerously rampant growth habit of Japanese honeysuckle. Some options include:
- Goldflame honeysuckle (Lonicera heckrottii) is a deciduous vining plant that is hardy in zones 5 to 9. Growing to 15 to 20 feet, it has fragrant flowers that are hot pink with yellow throats, blooming from late spring through mid-summer.
- Dropmore scarlet honeysuckle (Lonicera brownii) is hardy in zones 3 to 9. It is a smaller vine, growing to 12 feet, and produces fragrant bright red flowers from late spring through mid-summer.
- Trumpet honeysuckle (Lonicera sempervirens) is a semi-evergreen vine that is hardy in zones 4 to 10. It grows to 12 feet and has bright orange, red or yellow, tubular flowers from late spring to mid-summer.
- Henry's honeysuckle (Lonicera henry) is hardy in zones 4 to 10. It grows to 30 feet and has red or yellow tubular flowers through spring and summer.
- American honeysuckle (Lonicera americana) is hardy in zones 6 to 10 and grows to 25 feet. It has scented yellow flowers tinged with red, pink, or purple from late spring into fall.
- Winter honeysuckle (Lonicera fragrantissima) is a semi-evergreen shrub form that grows to 10 feet tall with a similar spread It is hardy in zones 4 to 8. It has pairs of small, creamy white, fragrant flowers from late winter through mid-spring.
Common Pest and Diseases
Japanese honeysuckle is largely without serious insect and disease problems, as befits a vine with a reputation for being vigorous to the point of being invasive.
The main problem with Japanese honeysuckle is controlling the plant or eliminating plants that escape cultivation and naturalize where they are unwanted. Japanese honeysuckle is listed as an invasive plant as far up the East Coast of the United States as the southern parts of New England. It is a true menace in parts of the country where the foliage is evergreen and thereby more vigorous. In the South, Japanese honeysuckle grows so aggressively that its weight poses a danger to trees when it climbs into their canopies. The plant can also harm shrubs and small trees by girdling them.
In northern New England and other similar climates, Hall's Japanese honeysuckle is unlikely to spread so aggressively. Check with your local county extension to inquire about Japanese honeysuckle's invasive status in your area.
If you have only a few unwanted vines, cut them down to ground-level in late summer, then coat the cut ends with undiluted glyphosate (Roundup) liquid. Large areas of honeysuckle should be mowed down as close to the ground as possible. When new growth begins to sprout, coat them with a 5 percent solution of glyphosate.