Common Name: English Ivy
Scientific Name: Hedera helix L.
Code: HEHE
Group: Dicot
Growth Habit:Vine/Subshrub
Duration: Perennial

CAUTION: Compounds in English ivy include glycosides, which are toxic and can cause vomiting, diarrhea, nervous conditions and dermatitis in some individuals (Swearingen and Diedrich 2000).

What does it look like?

English ivy is a common groundcover with dark green, waxy leaves that become more rounded in shape as it climbs trees. The leaf form consists of a 3-lobed leaf with a heart-shaped base, while leaves in full sun are often unlobed, oval, and have wedge-shaped bases. Leaves are arranged alternately along stems. Flowers resemble umbrella-like clusters of small, greenish-white flowers that appear in the fall with sufficient sunlight. The fruits mature in spring and are black with a fleshy outer covering around one or a few hard seeds (Swearingen and Diedrich 2000).

Where does it grow?

English Ivy is native to Europe, western Asia and northern Africa, but is now widely distributed throughout the United States and still commonly used in landscaping. English Ivy is one of the few invasive plants that can become established in deep shade (NPS, 2001). It generally inhabits woodlands, forest edges, fields, coastal areas, salt marsh edges, and other upland areas with some soil moisture. It does not like extremely wet conditions and generally grows in areas associated with some type of land disturbance.

Is it in our watershed?

There have been a few observations of English ivy growing in the Mattole, just off Chambers Road near Petrolia. The ivy was observed growing on a few trees in a small area, and should be eradicated immediately to prevent its spread.

What problems does it cause?

English ivy is an extremely aggressive invader that threatens all types of vegetation in forested and open areas, due to the fact that it can grow on the ground AND in forest canopy. This plant smothers shrubs, groundcover, and even the tallest trees, including redwoods (BLM 2003). The vines also often weigh down tree branches, causing them to break, harming the integrity of many forest ecosystems.

English ivy also prevents regeneration in forests by killing many trees in the understory and overstory by shading them out. In deciduous trees, the increased winter light allows the vine to grow rapidly upward towards the canopy in the winter months (Thomas 1980, as cited in Bossard et al. 2000).

How do you get rid of it?

Manual/Mechanical Control: It is most important to begin removal of the plants that are in the climbing growth stage—“aerial” plants. These are the easiest to kill and the most threatening because they produce seeds that birds disperse, leading to large ranges of infestation. To remove, “girdle” the tree, carefully so to not kill the tree, but make sure to cut through the stems of the ivy (BLM, 2000). You can also use pruners to cut the vines from down from the trees.

Plants spreading on the ground are usually not yet seeding. At this stage, pull up from the roots repeatedly, with persistence, and it will eventually die. Be sure to watch for seedlings that can sprout from the seed bank.

Biological Control: There are no biological controls currently available for English ivy (Swearingen, 2000).

Author:
Unity Peterson, Invasive Plant Program Coordinator, Mattole Restoration Council, Petrolia, CA.

Photographs:
Unity Peterson

References:
BLM 2000. Noxious Weeds of the Arcata Field Office. Bureau of Land Management. http://www.ca.blm.gov//arcata/arcweeds.html

Bossard, CC., J.M. Randall and M. Hoshovsky. (eds.) 2000. Invasive Plants of California’s Wildlands. University of California Press, Berkeley, CA. Online version: http://groups.ucanr.org/ceppc/Invasive_Plants_of_California's_Wildlands/

NPS 2001. Exotic Plant Species List. Scientific and Common Names of known Exotic Plant Species in the Redwood National and State Parks. National Park Service. http://www.nps.gov/redw/epsplist.htm

Swearingen, Jill M., US National Park Service, Washington, DC. 2000. English Ivy. Plant Conservation Alliance. http://www.nps.gov/plants/alien/fact/hehe1.htm