Invasive Species of the Day: English Ivy
English Ivy (Hedera helix) has been used in cultivation for centuries, but in areas where it is not native, it can be a very problematic plant.
Origin: Europe, Western Asia and Northern Africa
Background
European colonists introduced English ivy as early as 1727. It is widely planted for its evergreen foliage and dependability as a year-round “carefree” groundcover. Although recognized as a serious weed of natural ecosystems, parks, landscapes and other areas, it continues to be sold and marketed as an ornamental plant in the United States. Vast resources, time and labor are expended attempting to manage infestations on public and private lands.
Distribution and Habitat
English ivy is found throughout the eastern U.S. and in the West where it occurs from Arizona to Washington State. It flourishes under shady to full sun conditions in soils that are moderately fertile and moist but it is intolerant of drought and salinity. Habitats invaded include forest openings and edges, fields, cliffs, steep slopes, and disturbed areas.
Ecological Threat
English ivy is an aggressive invader that threatens all vegetation levels of forested and open areas, growing along the ground as well as into the forest canopy. Vines climbing up tree trunks spread out and envelop branches and twigs, blocking sunlight from reaching the host tree’s foliage, thereby impeding photosynthesis. An infested tree will exhibit decline for several to many years before it dies. The added weight of vines also makes trees susceptible to blowing over during storms. English ivy has been confirmed as a reservoir for bacterial leaf scorch (Xylella fastidiosa), a harmful plant pathogen that affects a wide variety of native and ornamental trees such as elms, oaks and maples.
Description and Biology
Plant: evergreen perennial climbing vine that attaches to bark of trees, brickwork and other surfaces by root-like structures that exude a glue-like substance to aid in adherence.
Leaves: alternate, dark green, waxy, somewhat leathery; extremely variable leaf forms, from unlobed to 3-5 lobed; typically green with whitish veins.
Flowers, fruits and seeds: flowering occurs in late summer to early fall, typically under full sun conditions; flowers are small, greenish-yellow and occur in globular starburst type inflorescences at tips of flowering stems; fruits are black with a fleshy outer layer and stone-like seeds.
Spreads: vegetatively by vigorous growth at tip of stems; and by seed which is consumed by birds and dispersed to new areas; fruits contain glycosides that may be mildly toxic and cause some birds to regurgitate them; new plants grow easily from cuttings or stem fragments that make contact with the soil.
Look-alikes: Irish ivy (Hedera hibernica), Persian ivy (Hedera colchica), Boston ivy (Parthenocissus japonicus) and Virginia creeper (Parthenocissus quinquefolia). Poison ivy (Toxicodendron radicans) may sometimes be confused with English ivy because of its hairy stems but because it is deciduous, it will lack leaves in the winter. In summer, poison ivy can be distinguished easily by its compound leaves of three leaflets and its clusters of creamy white fruits.
NOTE: The leaves and berries of English ivy contain the glycoside hederin which may cause toxicosis if ingested. Symptoms include gastrointestinal upset, diarrhea, hyperactivity, breathing difficulty, coma, fever, polydipsia, dilated pupils, muscular weakness, and lack of coordination. This feature also helps ensure effective seed dispersal by birds.
Prevention and Control
Do not plant English ivy including invasive cultivars. Individual vines can be pulled by hand when soil is moist. Vines covering the ground can be uprooted and gathered using a heavy-duty rake, then close to the ground with pruning snips, Swedish brush axe or other cutting tool. Gathered vines can be piled up and allowed to desiccate and rot which will occur quickly, in a matter of days. If needed, material can be bagged and disposed of in normal trash. Vines climbing up trees can be cut a few feet from the ground, for convenience, to kill upper portions and then apply systemic herbicide to lower cut portions
Source:
National Parks Service http://www.nps.gov/plants/alien/pubs/midatlantic/hehe.htm