The snow has melted and the natural world is coming back to life: we are too. Gardeners eagerly plan their masterpieces. Anglers and paddlers take to the water, hikers to the trails. Migratory birds return and serenade. Spring flowers delight. Amidst this idyllic scene is another suite of species, however, putting at risk the ecological benefits and recreational pastimes of the region: invasive species.
Early and fast growth, apparent at this time of year, helps make these interlopers successful. Invasive plants are among the first to green-up in the spring and often the last to remain in the fall, giving them a competitive edge over native plants.
Honeysuckle (Lonicera spp.) is one invader obvious now. Leafing out in April, its foliage fills in by May. As recently as the 1980s, honeysuckles were promoted for their wildlife values, ornamental use and soil stabilization. But, over time, honeysuckle became another case of a good plant gone bad.
Honeysuckle at the forest edge
(Photo courtesy of APIPP)
Adaptable to a variety of habitats ranging from forests to fields and roadsides, honeysuckle is widespread in both cultivated and natural areas across the Northeast. It tolerates various moisture and light levels and can be an aggressive colonizer. Forming a dense layer that shades the ground, it interferes with the growth of many native woody and herbaceous species: a honeysuckle thicket is often void of other vegetation.
Many varieties are popular landscape plants that originated in Europe and Asia. Amur (L. maackii), Morrow's (L. morrowii), Tartaria (L. tatarica), Fly (L. x bella) and European fly honeysuckles (L. xylosteum) are invasive shrub honeysuckles. Woody perennials, they grow from 6-15 feet in height, appearing weak and twiggy with widely spreading branches and grayish, shaggy bark. Elliptical leaves are oppositely arranged on the stem. Tubular flowers in May and June range from whitish yellow to pale and dark pink. Red fruits produced in mid-summer appear in pairs along the stem.
Unlike the shrub honeysuckles, Japanese honeysuckle (L. japonica) is an invasive woody, perennial vine growing to 30 feet that produces dark purple to black fruit. It spreads locally via runners. Both shrub and vine honeysuckles are prolific fruit producers and widely dispersed by birds.
Removing honeysuckle is easier than removing other invasive plants. Seedlings are easily pulled, or, for larger shrubs, a weed wrench helps pop the shrub up by its roots. Controls are best done in the spring when soils are wet and roots are not well established. Any treatment that involves cutting should be done in early spring and in late summer or early fall. Cutting of plants results in resprouting, but is effective in temporarily reducing seed production. Shrubs can be left to dry (if without fruit) or taken to the transfer station. As with many invasive plants, control methods may need to be repeated for three to five years to inhibit resprouting and to exhaust the seedbank.
Unlike invasive non-native honeysuckles, the native honeysuckles found in the region are not problematic spreaders. Established here for thousands of years, they have predators that keep their population levels in check. Northern bush-honeysuckle (Diervilla lonicera), American fly-honeysuckle (Lonicera canadensis) and Limber honeysuckle (L. dioica) are native to Adirondack woodlands. Honeysuckles typical of fens and wet areas include Mountain fly-honeysuckle (L. villosa) and Swamp fly-honeysuckle (L. oblongifolia). Native vines include Trumpet honeysuckle (L. sempervirens) and Hairy honeysuckle (L. hirsuta).
One way to differentiate between the invasive shrub honeysuckles and the natives is that the twigs of non-native honeysuckles have hollow stems, while the stems of the natives are solid. Also, the introduced honeysuckles grow much larger and more robust than native honeysuckles.
Just because a plant is not native does not mean it will be a problem; only a small percentage of non-native plants are harmful but they can cause long-term and irreversible damage. Learn which species pose the greatest threat to your area and be an informed consumer when buying ornamental plants. A tag may read "honeysuckle" or "Lonicera" but may not be enough information to know whether it is invasive or not. Know the specific species name if possible. If you notice nurseries selling invasive plants, request that they offer non-invasive choices. Even the most well intentioned plantings can become garden escapees.
Eye on Invasives is a biweekly column that spotlights a top invader when it is easiest to identify. Hilary Smith directs the Adirondack Park Invasive Plant Program, a partnership program housed at the Adirondack Chapter of The Nature Conservancy in Keene Valley. Find out more about this award-winning program online at www.adkinvasives.com.