English Ivy: An Invasive Species in Seattle's Forests

Ivy invaded forest in Bellevue, Washington

English ivy has become a major invasive species in the Pacific Northwest, from British Columbia to California. English ivy is not native to the United States and has no natural predators or pests to keep it in check. It easily escapes from planting areas and invades natural areas, parks and urban forests. English ivy suppresses and excludes other vegetation to form a dense monoculture groundcover, unsuitable as wildlife habitat. As a vine, it can completely engulf shrubs and encircles tree trunks of all sizes, leaving nothing uncovered. Shrubs shrouded in ivy may eventually die because light can't reach their leaves. The sheer weight of the extra vegetation also weakens the plant it grows on, making it more susceptible to disease and blowdown. It grows rapidly and needs very little light or water once it's established. It spreads rapidly as a groundcover and also climbs as a vine. Seattle’s trees are aging and overwhelmed with English ivy. English ivy is an additional threat as it climbs up into the canopy causing trees to fall in high winds. Over the years, English ivy began to establish under the canopy of Seattle’s forest. In many parks the invasive plant now dominates and covers the ground, blocking the potential for all native trees to naturally regenerate. Since then, the leafy trees have grown large and old and are nearing the end of their natural life. The ivy is an invasive plant and over time will kill these trees by robbing them of nutrients.

What can you do?

Do not plant ivy. Remove ivy, especially from vertical surfaces where it seeds and is spread further by birds. Remove ivy from your yard. Join community out-reach and volunteer-based removal work parties. Visit http://www.ivyout.org/ for more information on how you can help in the fight against English ivy.

http://greenseattle.org/about/the-problem

http://extension.oregonstate.edu/gardening/node/948

http://www.ivyout.org/

                                                                                     Written by Isabella Kharrazi