What a beautiful show Fall gave us this year! I don’t know about you, but I couldn’t keep my eyes off the brilliant reds, yellows, and oranges that decorated Benton County. Alas, as all the leaves fall and many native species go dormant for the winter, the plant that continues to catch my eye is…you guessed it! Ivy!
Ivy (Hedera spp.) is an incredibly invasive species here in Oregon. Ivy creates a dense monoculture mat of vines that suffocates shrubs and shades out native vegetation. Native species, which often have deeper root systems, are out-competed by this shallow rooted plant, increasing chances of erosion. Ivy climbs up trees and can weigh them down to the point that the trees die and fall over, destroying critical woodland and riparian habitat.
Wintertime is the perfect time to tackle your ivy issue because the native species like snowberry and bleeding heart have gone dormant for the winter. Ivy, as you may have noticed, does not go dormant so it is easily accessible for winter control. The interesting thing about ivy is that it is a totally manageable species, albeit one that takes some hard work.
When working to remove ivy, it’s important to think through the biology of the species. It’s a plant that only seeds after it has climbed up a structure. All the ivy you see on the ground is only spreading through runners, not actually establishing new plant populations and spreading! Once ivy grows up a structure, such as a tree, it goes to seed and can spread through wind and animal dispersal.
As you begin to tackle ivy on your property, first check out our pamphlet on managing English ivy. Prioritize the ivy growing up structures (also known as aerial ivy). A good way to control tree ivy is using a method called gapping. Use a sharp object (pruners or a machete) to cut all the way through the ivy vines circling the tree at chest height. Once you have cut a ring around the tree, start by pulling the ivy off the tree and as far back from the tree as you possibly can. The ivy above the cut will wither and die. Contractors will sometimes cut the gap of ivy then paint herbicide on the tips, ultimately killing the ground ivy at the same time. If you choose to do this, make sure you read and follow all herbicide labels. If you can only treat minimal amounts of ivy, make sure to prioritize the tree ivy to keep the seeds from spreading!
Once you’ve tackled the aerial ivy, you can begin on the ground ivy. You can pull ivy by hand out of the ground, again with winter being the optimal time. During the winter the soil is moist and loose, making hand-pulling easier than in summer when soil is hard and dry. Cut a line in the ivy mat, pulling apart each side of the mat as you go. Start to lift the mat and pull the cut edge of the vines then roll the ivy mat over itself. Try to roll it up like a carpet. Remember that piling ivy will not kill it, runners will slowly creep out, so the entire plant needs to be disposed of. This can be accomplished through bagging, burning, or using herbicide. If you choose to use herbicide, try to use it in the winter to protect native species and make sure to read and follow all herbicide labels.
A final option is to smother the ivy. This involves at least eight inches of mulch directly over the ivy. Laying cardboard before mulching increases the effectiveness. It’s recommended that this stays in place for at least two years before attempting to replant.
We’ve been working hard here at Benton SWCD to control ivy in Benton County. Through our partners with the Willamette Mainstem Cooperative and the Benton County Cooperative Weed Management Area we have treated over four miles of riparian ivy along the Highway 20 stretch between Corvallis and Albany and hosted ivy pulls through our annual Let’s Pull Together event. We worked with Philomath High School to pull ivy from two parks in Philomath, and with City of Albany Parks and Recreation Department and Calapooia Watershed Council to pull ivy from two parks in Albany. We’ve even worked with goats to try and tackle the problem! The impacts of ivy are detrimental to our Benton County habitats, and we all can do our part to control it in our areas.