English Ivy (Hedera helix): Beloved Ornamental or Invasive Threat?

Few plants evoke such polarized feelings as English ivy. Its romantic drape over cottage walls and the iconic outfield of Wrigley Field (actually Boston ivy, Parthenocissus tricuspidata) contrast sharply with its reputation as a garden thug. True ivies belong to the genus Hedera, with Hedera helix being the most common.

History and Symbolism

Ivy has ancient roots. It crowned Dionysos and his bacchantes, who carried ivy-wrapped thyrsos staffs. Before discovering grapes, the god supposedly ate toxic ivy berries for intoxication. Later, ivy became a Christmas evergreen symbol, though it plays second fiddle to holly in carols.

Growth Phases

Ivy exhibits two distinct phases:

• Juvenile: Woody climbing evergreen vine with aerial rootlets; leaves palmate, three-lobed. This is the familiar groundcover/climber form.
• Adult: In full sun, mature ivy develops a thick trunk without aerial roots, heart-shaped leaves, and insignificant flowers that yield small black berries.

Why Gardeners Plant It—and Why They Regret It

Ivy thrives in deep shade where little else grows, making it a popular groundcover for north-side foundations and beneath trees. Cultivars offer variegated foliage for containers and houseplants. However, its vigor becomes a liability: as a dense groundcover it smothers native plants; as a climber it can damage walls and trees. It ranks #8 on Dave's Garden's "Top Ten Thugs" list, drawing vehement criticism.

Control and Eradication

Once established, ivy resists removal. Waxy leaves repel herbicides; woody roots resist pulling and resprout from fragments. The most effective method (short of mechanical excavation) is painting cut trunk/root surfaces with a strong brush-rated herbicide.

Ecological Impact

Birds spread berries into wild areas, where ivy carpets forest floors, outcompeting native vegetation. Oregon and Washington list H. helix and cultivars like H. hibernica and H. baltica as noxious weeds. In warmer climates, massive vines compete with host trees for light and can pull them down.

Climate Makes the Difference

In Zone 5, a cold snap freezes climbing growth, naturally checking ivy's ascent. The author maintains a trouble-free bed beneath junipers with annual trimming. Conversely, in the damp, freeze-free Pacific Northwest, ivy becomes monstrous—justifying its "thug" label. Context dictates whether ivy is a charming accent or an ecological menace.

Photo credit: Ivy on tree © 2005 by Nate Steiner, CC BY 2.0