Extension Service Garden Hints

English ivy listed as a noxious weed

CORVALLIS - The latest addition to the state's noxious weed list is ironically one of the most common and popular ornamental groundcovers, according to Jed Colquhoun, weed scientist at Oregon State University Extension Service. It is English ivy.

"Unfortunately, the same biological characteristics that have led to ivy's popularity have also caused it to become a troublesome invader," Colquhoun pointed out.

English ivy (Hedera helix) is a woody, evergreen vine that grows rapidly with roots along the stem that allow the plant to cling to walls and climb trees. It is very long-lived, often taking up to 40 years to reach maturity and blossom. Flower clusters produce small black berries that are toxic to several animals.

English ivy was introduced to North America from Europe and Asia as an ornamental groundcover. Today, more than 40 cultivars are commercially available. In Oregon, several nurserymen produce English ivy and hundreds of retail nurseries sell it.

"As an aggressive and rapid competitor, English ivy provides a solid, weed-free groundcover that requires little maintenance," said Colquhoun. "Unfortunately, plants that escape ornamental management compete and displace native plants, particularly in forested areas. Not only can English ivy compete for resources, but it can also topple trees due to the sheer weight of the plant biomass that clings to trunks and branches."

Removal of English ivy where it is not wanted requires an integrated approach, according to Colquhoun.

"Because it is shallow-rooted, the plant is easily pulled and small areas can be controlled effectively with manual removal," said Colquhoun. Chemical control is less effective and poses the danger of drift onto nearby desirable plants.

"Repeated applications of 2,4-D or glyphosate may provide moderate to good control in large infested areas. As with any pesticide, always consult and follow the label prior to application," he said.

The commercial availability of a noxious weed is a bit ironic, according to Colquhoun. "The resources utilized to develop and commercialize English ivy are counterbalanced by the resources committed to eliminating escaped plants. In the current situation, eradicating English ivy is like trying to fill a water trough with a hole in it."

By: Peg Herring
Source: Jed Colquhoun

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