Ecology Distribution Management Info Impact Info References and Links Contacts

General Impact According to Diedrich and Swearingen (2000), Hedera helix 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. The impacts of H. helix include decrease in native vegetation and loss of biodiversity. The dense growth and abundant leaves, which spring from the stems like small umbrellas, form a thick canopy just above the ground and prevent sunlight from reaching other plants. Vines climbing up tree trunks spread, surround and cover branches and twigs, preventing most of the sunlight from reaching the leaves of the host tree thus reducing photosynthesis. It cover meristems, and thus disrupt the tree's growth, first on branch tips and eventually at the tree top. The impacts on photosynthesis and growth may well produce parallel damage to the root system, since the tree can no longer provide the level of nutrition to the roots (David L. Morgan in Aliens-L January 28 2005). Loss of host tree vigor, evident within a few years, is followed by death a few years later. The added weight of vines makes infested trees susceptible to blow-over during storms.          Location Specific Impacts: Garry Oak Ecosystems (Canada) (Canada)   Damage to host species: H. helix may create a dense cover on the bark of trees, depriving the bark of normal contact with air and micro-organisms. The weight of the vine and leaves, together with moisture from rain and snowfalls, makes the tree top-heavy and prone to damage or blowdown during windstorms. Heavy ivy cover may eventually reduce the tree’s foliage and its capacity to photosynthesise, weakening or even killing the tree. Habitat alteration: The dense growth habit of H. helix and abundant leaves can block sunlight from low-growing native plants, crowding them out and preventing germination of their seeds. H. helix may eventually dominate excluding most plants on the forest floor, and altering or eliminating habitat and food sources for many birds, mammals, butterflies, and other wildlife.