Invasive: English ivy is growing problem

A few weeks ago Pat Eisenach wrote me that she is concerned about the spread of English Ivy.

"I have noticed more and more trees that are being covered by ivy; in yards, in city parks, in Reynolda Garden's natural areas. Last fall, I was walking on the paths through Miller Park and noticed it on some trees only about 10 to 20 feet high, so it seems like a relatively new phenomenon that's being allowed to happen in some places. Is the Winston-Salem Recreation and Parks Department not maintaining our parks?"

Eisenach voices a legitimate concern. English ivy and other invasive vines are rampant in many parts of the city. They are making many of our natural areas not so natural.

English ivy can be blamed for many problems.

"English Ivy is a vigorous growing vine that impacts all levels of disturbed and undisturbed forested areas, growing both as a ground cover and a climbing vine," the UDSDA's Plant Conservation Alliance Alien Plant Working Group states in its fact sheet on English Ivy. "As the ivy climbs in search of increased light, it engulfs and kills branches by blocking light from reaching the host tree's leaves. Branch dieback proceeds from the lower to upper branches, often leaving the tree with just a small green ‘broccoli head.' The host tree eventually succumbs entirely from this insidious and steady weakening."

"One of the problems is the weight," said Keith Finch, the urban forester for the city. "It also blocks out sunlight, competes for nutrients and harbors insects. We try to cut English ivy from trees in parks. If it is prominent, we try to deal with it. We would probably address it a little more aggressively if we had more manpower."

Ivy is well established in the woods surrounding Reynolda Gardens of Wake Forest University, where I count myself among the staff.

"We are not sure how we are going to approach the issue at this point" said Preston Stockton, the Reynolda Gardens manager. "We have hired a landscape-architecture firm that is looking at the invasive issue along with several others as they draft a cultural-landscape report," Stockton said.

James Mitchell, Winston Salem's director of vegetation management said: "We don't have an explicit policy for removing ivy from trees, but if we are working in an area where it is bad, we try to address it. We don't have the manpower to target specific areas."

Ivy is a problem plant throughout the Southeast and mid-Atlantic. But in the Northwest it has become a major scourge, spawning citizen-driven eradication campaigns such as the No Ivy League. The No Ivy League works in Oregon's Forest Park in Portland. It is the largest urban forest in the U.S.

Established in 1994, the No Ivy League has removed over 267 acres of English Ivy from the park and organized over 200,000 volunteer hours.

Cutting, grubbing, pulling and digging are the most effective and immediate ways to deal with ivy. It can be hard work and often needs to be repeated.

English ivy has been known to cause a contact dermatitis in some people, so caution should be used when handling it. Cutting the vines in a band at the tree trunk will kill the ascending growth, but it will not fall on its own, remaining brown and unsightly unless removed by hand.

The commonly available Round Up herbicide may yield a partial burn. But it rarely controls the vine. Applying Round Up while new growth is emerging and tender can be effective. Unfortunately, desirable vegetation is emerging at this time also, and is equally or more susceptible to the effects of the herbicide. Brush killer systemic herbicides containing triclopyr amine are effective when painted on the cut stems.

Most important, the vines should be removed from the trunks of trees. The US National Arboretum states on its Web site that "English Ivy only reaches maturity and goes to seed after it has grown up a vertical surface." Mature vines bear blue fruit that are mildly toxic to humans but readily spread by birds.

English ivy is a gardener's paradox. The very things that make it a desirable garden plant -- its rapid growth, lack of pest and disease problems, and ability to suppress competing plant growth -- are what make it a nightmare in our native forests.

If you have a gardening question or story idea, write to David Bare in care of Features, Winston-Salem Journal, P.O. Box 3159, Winston-Salem, NC 27101-3159, or send e-mail to his attention to gardening@wsjournal.com.