Focus on invasive species: English Ivy

English ivy (Hedera helix L.) is a creeping evergreen vine native to Europe. It has been traditionally planted as groundcover or wall covering because it retains its summer color throughout winter months when everything else is brown or leafless. It is a common sight on lawns, in garden beds, and on brick and stone walls. It attaches itself by adventitious aerial rootlets, which exude a sticky glue-like substance. The leaves of English ivy are evergreen and are found in a variety of shapes from tri-lobed leaves in the shade and on newer growth to unlobed forms in the sun. In the fall, clusters of small, greenish-white flowers are present when there is adequate light. The fruits, which form in the spring, contain stone-like seeds and are mildly toxic.

English ivy is an aggressive invader and, once established, quickly blankets the ground and can climb into the tree canopy. Because it's evergreen, it can photosynthesize long after most native plants have gone into dormancy in the fall and can grow throughout the winter. The adventitious rootlets have been know to work their way into the mortar of walls and reduce vigor of host trees. Furthermore, the added weight from the vines can be enough to pull branches down and tear apart walls. Once established, this plant is hard to control and, therefore, should not be used in horticultural plantings. Removal of this species from a site may require a lot of muscle. Eradication from sites can be very time consuming and may require the use of herbicides. In short, this species can threaten our native plants and animals and should not be grown where it might escape.

For more information on ways to control this aggressive invader, check out the National Park website “Weeds gone wild,” which provides comprehensive information on English ivy, and other nasty non-native invaders: http://www.nps.gov/plants/alien/

Today's photo is by Ephraim Zimmerman.

Reference: Plant Conservation Alliance, Bureau of Land Management.

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