At last week's Master Gardener Plant Clinic I was speaking with a local gardener who mentioned she was cultivating English Ivy in her Newport garden. After gently mentioning that English Ivy is an invasive, noxious species in Oregon and discussing why the plant is so troublesome for Oregon forests, I still failed to convince her to change course.
What I didn't know at the time was that English Ivy was banned by the State in 2010 and cannot be transported, sold or propagated. Oregon did not go so far as to make it a crime to plant English Ivy; nor is removal required but of course most folks will want to do so voluntarily.
It is simply not safe to have English Ivy on our properties because it is virtually impossible to keep the ivy from spreading. The plant is spread by birds who eat the seed and drop them in other places. Our coastal winds will also disperse the seeds across large tracts of land. English Ivy is more shade, drought, disease, and insect tolerant than any of our native plants. It is poisonous to most animals so offers nothing in the way of wildlife support. Take a quick look around as you drive through the county and you will see many examples of ivy climbing trees and producing such dense matting that no other plants can survive or take hold. Trees start to smother when the ivy covers about 2/3 of the trunk. Think of the birds and animals that can't find local seeds or nesting habitat because the ivy has become so pervasive.
What to do
1. To protect your trees, cut the ivy at the top and bottom of the trunk. We usually focus on ankle and shoulder height as a good estimate for cutting. Be sure to get all the the vines surrounding the tree. Don't cut into the tree trunk to avoid girdling the tree which will kill it.
2. Mark or take notice of local plants that are still growing among the ivy. You may want to create a space around these to protect them especially if you choose to apply a pesticide to help kill the ivy. Many native ground covers, such as trillium, lilies, and piggyback, go dormant so clearing a border will make it easier to remember where they are located.
3. If you apply pesticide, be sure to read the instructions, wear appropriate clothing, and choose a day that is not too hot or cold and not too windy.
4. Persevere and be patient. Whether you cut, pull, dig or poison these invasive plants, it will take a year or two to be rid of the original plants and a few more years culling out new seedlings .
Check out the OSU fact sheet for removing English Ivy.