English Ivy

How does an inexpensive, easily propagated vine start out as a garden basket filler and become a noxious weed, climbing trees, smothering understory plants and tree seedlings in our yards, natural areas and parks?

English ivy is cheap (to buy) and easy (to grow), and it reportedly lives to a ripe old age of 400.

It is native to Europe and Asia, with a long history as a garden plant. Several ivies are mentioned in 314 B.C. in Historia Plantarum! It is still a popular garden plant, with over 400 recognized cultivars. Considered noxious in Washington: English ivy cultivars (Hedera helix ‘Baltica’, H. helix ‘Pittsburgh’, H. helix ‘Star’ and H. hibernica ‘Hibernica’). They love our climate and our natural areas, where they grow for 9 to 10 months a year.

English ivy appeared in the Pacific Northwest sometime in the 1890s. Nothing stops ivy—there are no predatory insects or animals and our winters are not harsh enough to kill it. Birds spread the dark colored berrylike fruits in the early spring, when food is still scarce. The combination of a long-lived vine thriving in our climate and a century of new introductions has contributed to the unchecked spread.

English ivy is invasive when growing in areas where it was not planted. The immature vines climb trees, fences, small buildings and whatever else gets in the way with adhesive pads at the root tips. Immature plants do not produce flowers and fruit, but new plants grow from very small stem pieces.

Older vines grow over 90 feet long with stems reaching one foot in diameter. Creeping vines smother smaller plants and seedlings before winding their way up trees. Ivy adds weight to trees—one tree had 2,100 pounds of ivy removed. With rain, ice, dirt and debris the load gets too heavy for trees, and wind and rain may pull a weighted tree down.

The shallow roots of English ivy make it a poor choice for erosion control. English ivy mats on the ground or hangs onto buildings, hiding rats, holding water and creating areas of still air – a good hiding spot for mosquitoes. Something to think about with concerns of West Nile Virus.

Because of the impacts, the four English ivy cultivars were listed as a noxious weed in Washington in 2002. It is a Class C Noxious Weed of Concern in King County - control is strongly encouraged although not currently required, and new plantings of invasive cultivars are discouraged.

Avoid buying and planting invasive cultivars. Cut any flowers to stop further spread by seed. Hand pull or dig out accessible plants. Cut or pry vines off of trees—the upper vines will die, remove the rooted part. Remove all cut stems from soil contact.

For more information on English ivy, on noxious weeds, or noxious weed laws, please contact the King County Noxious Weed Control Program. (206) 296-0290 or visit http://dnr.metrokc.gov/weeds.