Controlling English Ivy
Controlling English Ivy
Why Not English ivy?
Everyone knows English ivy. It's that easy-to-grow vine with the "ivy-shaped" leaves that you plant as a ground cover and forget about. It rarely gets any bug or disease problems, can often get by without water in summer, can grow in deep shade, and stays green year-round.1 What's not to like?
The problem is that sometimes it's a little too easy to grow. In a number of states English ivy (Hedera helix)has moved from people's gardens and invaded nearby parks, forests and other natural areas.1,2 Left unchecked, it can create "ivy deserts" - large sections of solid ivy where no other plants can grow. Ivy kills trees by climbing into their canopies and shading out sunlight, and also making them so top-heavy they can blow over. Dense ivy destroys habitat for native wildlife and creates an ideal refuge for rats.1 Not quite so nice as you may have thought.
In Oregon and Washington, English ivy has landed on state lists of noxious weeds. Washington has identified four cultivars as having invasive tendencies (see sidebar for names and photos), and control and education efforts are left up to the counties.3 Oregon bans the sale and import of generic English ivy (Hedera helix).4
There are hundreds of named varieties of ivy5, but buying a well-behaved variety can be tricky because some ivy plants are mislabeled at garden centers.6 If invasive ivy is a problem in your area, you can help protect natural areas by seeking out alternatives to English ivy so as not to endanger the health of the local ecosystem.
English ivy is a woody perennial vine that comes in two distinct forms: juvenile and mature. Juvenile leaves are the classic "ivy" shape, are glossy and dark green with whitish veins that are deeply lobed and usually between 1 1/2 inches and 3 inches in size. The juvenile form can make roots at almost any place the stem nodes touch the ground, enabling the plant to spread easily.1,5
When juvenile plants bump into a vertical surface they start to climb, attaching their rootlets with a glue-like substance. Ivy may spend ten years in its juvenile form, but at some point the plant switches to the mature form.1
Leaves of the mature form are a lighter green color, unlobed or slightly lobed, and thicker with less visible veins.1,5 The mature stage plant produces flowers, fruits and seeds. Birds contribute to the spread of ivy by dispersing seeds to new areas.1
Manual Removal is Best
To reign in ivy on your property, manual removal is the most effective method of control, according to the Noxious Weed Control Program of King County, Washington.5 and no getting around it, this means lots of physical labor. By approaching this methodically, you will maximize your efforts. Be aware that the sap can cause itching and blistering on some people, so be sure to wear gloves and long sleeved shirts and pants while working with it.5
Mowing and mulching are other alternatives. Regular mowing will keep ivy under control.5,7 You can put an 8-inch layer of mulch directly on top of plants.
Key Points from The Ivy Removal Project
The Ivy Removal Project (also known as the No Ivy League) offers the most detailed resource for ivy removal techniques. If you are looking beyond your own yard toward community efforts to control escaped ivy, see http://www.noivyleague.com/.
Here are some key steps that will help homeowners tackle ivy:
Stop seeds from spreading. Your top priority should be stopping seeds from spreading by targeting mature-form ivy wherever you find it. Around your home, prioritize your efforts by tackling mature ivy on trees first, and then removing it from any buildings. Ivy can contribute to rot and deterioration of structures.7
There is no need to remove ivy all the way up into the tree canopy. This can be dangerous and is unnecessary. Instead, carefully cut all vines around the trunk at about shoulder height. The ivy above the cut can be left in place and will eventually die.7
If tackling mature stage vines isn't an immediate option, at least cut off any blooms and seeds within reach to prevent birds from spreading your ivy problem.
Save the trees. Below the girdling cuts, pull ivy vines away from the tree down to the ground and focus on getting out roots from around the base of the tree. The Ivy Removal Project recommends clearing the ground of all ivy in a circle that extends six feet out from the tree. This will help protect the tree from re-infestation for an extended time. If it is practical, by all means, continue removing all ivy from wooded areas of your property. Creating a "Lifesaver," or 6-foot circle around a tree, gives you the most bang for your buck. (See sidebar for details and photos).7
Be thorough. When pulling up English ivy, it is much more effective to work on a small section and to thoroughly remove as many roots as possible than to take a little bit from here and there. Thoroughly cleaned up areas are more easily defended from re-infestation. Starting from the end of a vine, pull off as much as you can and then go back and remove any pieces of vine and roots that may have been left. Various hand tools can help with this. Vines will come out much more easily if the soil is damp.7
English ivy disposal. For small amounts, it's best to let English ivy dry out and die before putting it out with yard waste or composting. Dry out stems and rootlets for at least a week or cook plants in a black plastic bag placed in the sun. Larger amounts can be rolled, balled up, or stacked, but rotate them to make sure they don't root.5,7
Plan on follow-up. It is simply unrealistic to think that one pass through an English ivy infested area will be enough to be ivy-free. Plan on monitoring at least every six months and rooting out any ivy that you find.7. For large areas that you want to replant, consider mulching for an extended period of time to suppress re-growth. Options include a thick layer of mulch, newspapers, and plastic.7
Alternatives to Ivy
Many good alternatives to English ivy for ground cover or climbing vines exist. Native plants are an excellent choice. Seek advice from a local nursery with qualified staff or contact your state's native plant society. (see sidebar)
- Nadal, E. S. Diedrich. 2003. Knowing the enemy; A botanical and ecological profile of Hedera helix (English ivy). Ivy Removal Project. http://www.noivyleague.com/Pages/english_ivy_paper_profile.html (link no longer active)
- Washington State Noxious Weed Control Board. 2001. Draft written findings of the Washington State Noxious Weed Control Board. http://www.nwcb.wa.gov/weed_info/Hedera.htm (broken link)
- Washington State Noxious Weed Control Board. 2007. Washington state noxious weed list. http://www.nwcb.wa.gov/weed_list/weed_list.htm
- Oregon Dept. of Agriculture, Plant Division. http://www.oregon.gov/ODA/PLANT/WEEDS/statelist2.shtml#B_list
- Simon, Bridget. 2004. English ivy - Hedera helix. weed bulletin - King county noxious weed control program. http://dnr.metrokc.gov/wlr/lands/weeds/bmp.htm (link inactive)
- Washington Native Plant Society. Ivy Out. http://www.ivyout.org/
- Resources from: No Ivy League Ivy Removal Project web site. Forest Park, Portland [accessed November 2010]
Stein, Dan. "Controlling English Ivy."
Eugene, OR: Northwest Coalition for Alternatives to Pesticides, November 2007. Links updated November 2010.
Photos courtesy of Stevens County Noxious Weed Control Board, WA.