My favorite candidate for eradication is English ivy. One of the worst pests around, this pesky creeper displaces native plants and harms host trees and shrubs. It also harbors rats and other rodents, not to mention slugs. Out with the stuff! Whenever I write about removing ivy, I get questions about whether removal is really necessary. It is confusing to read that ivy is a dreadful invader and then find it for sale at your local nursery.
The confusion arises because ivy gets treated as both a wonder worker and an evil weed. Garden books written back East or in Europe sound ivy’s praises as a ground cover and a climber. Nearly every nursery carries ivy, often in several colorful forms. These days, however, many nurseries also post small warnings with the ivy, mentioning its wicked ways. In some parts of the country, gardeners struggle to grow English ivy and cherish the fancy forms for their horticultural cachet. Shouldn’t we delight in our abundance of ivy, when it grows so well here? Well, no.
The problem is that plants display different behavior patterns in different parts of the world. Back home in Europe, where ivy has been growing for millennia, it is well behaved. Here, however, this comparative newcomer has taken over large sections of the urban and suburban landscape, from Vancouver and Victoria, British Columbia, down through California, where it continues to be the most popular ground cover sold. Ivy is also infiltrating our native woodlands.
This is a big problem because ivy is an opportunist that takes over ecological niches. It smothers native climbers like honeysuckle and clematis. It destroys native ground covers such as creeping dogwood and trilliums. Ivy adapts well to a wide range of conditions. That adaptability is what makes it and other weeds dangerous. It is, finally, on the noxious and toxic weed lists for both Oregon and Washington and is considered a serious problem in several other states.
Ivy’s popularity has long protected it from the noxious weed listing or quarantine regulation that its rampant tendencies might otherwise trigger. It sells well. It is also so widespread that many people simply feel that control would be unenforceable. This is shortsighted, because, without some regulation, the problem will continue to grow. Ivy has already created serious damage, not only in urban and suburban settings, but in the wild. In Washington’s national forests and parks, ivy infiltration causes what foresters call “ivy desertification,” where ivy vines choke out native plants, displacing smaller understory plants as the vines spread. Then they scale trees.
When ivy climbs, it changes character and leaf form. Virtually all of the many kinds of ivy—fancy-leaf, lace-leaf, variegated, and so on—develop the same adult form. A study done through Seattle’s Center for Urban Horticulture revealed that most ivy damage comes from the larger-leaved forms of Hedera helix and that the tiny lace-leaf forms are less destructive, even over time. However, all mature or arboreal ivy produces flowers and lots of fruit. Birds eat the fat, black ivy berries, processing them so effectively that little ivy sprouts can be found almost everywhere.
Europeans argue passionately that ivy can’t hurt trees, and, perhaps in Europe, it doesn’t. Here, however, when it gets a stranglehold on trees that are not adapted to its embrace, ivy can stunt growth. Arborists talk about hearing the “pop” as tree bark expands in relief when they remove girdling vines.
It may be true that ivy won’t hurt healthy trees, but environmental challenges like excess summer water from lawn runoff, air pollution, and acid rain have stressed most trees. The considerable weight of mature ivy can destroy a stressed tree. Like a sail, high-climbing ivy catches wind, causing even healthy trees to snap.
How to Remove Ivy
Where ivy covers a relatively flat area and you know what’s underneath it, mowing can be a good temporary control. In unfamiliar territory, it’s important to cut ivy (or any ground cover) with a machete or weed whacker before risking your mower. This initial clearing session will reveal any hidden hazards such as stumps, holes, or rocks that can seriously damage expensive machinery.
On steep slopes where mowing is dangerous, ivy can be trimmed with a weed whacker or brush cutter. Trimming once each year will keep ivy in its juvenile state, which means it can’t produce seeds. However, it can still get away quickly, and a lapse of even a few seasons can create an ivy wilderness. You may well be responsible enough to keep the ivy under control. But, if you move or sell your home, the next person may not be so responsible, and the potential problem will simply be passed along.
Thus, you should supplement mowing or trimming with a staged removal program. Plan to replace the ivy slowly. Each time you hold a removal session, don’t work for more than a few hours. During that period, stop each hour and do something that uses different muscles and motions. For instance, if you have been pulling ivy, stop pulling and chop the vines into pieces or stuff them into black plastic collection bags. Why? For many people, more than a few hours of vigorous, repetitive action like pulling ivy can lead to problems, such as a torn shoulder (rotator cuff), an exquisitely painful experience I’d like to spare you.
Here’s a little reminder list for ivy removal:
- Warm up first, stretching and loosening up all body joints.
- Actively pull ivy for no more than an hour (or less).
- Take a break and do something totally different for half an hour.
- Shake out your hands and shoulders every fifteen minutes.
- Remember that ivy removal can be done all year-round. An hour a week is plenty.
As ivy climbs, it becomes mature or arboreal. The leaf shape changes, and flowering and fruiting spurs appear. It is not, however, parasitic (able to live off the host plant). If you remove the bottom four to six feet of ivy from a tree trunk, the ivy on the tree will die. It takes about a year for the leaves to turn brown and several more years for the vines to fall off. But it happens naturally—at no cost.
To prevent re-growth, pull as much ivy root from the ground as possible. After the trees are set free, spend an hour or two each week removing ivy from the ground. A small pick or mattock works beautifully for this chore. This is also an excellent family project, and most kids really enjoy ivy removal days.
Two people can remove sheets of ivy quickly if one end is loosened with a sharpened edging tool or sharp, flat shovel. Start anywhere and make a long cut with the tool. Next, one person rolls the ivy back like a rug, and the other chops the roots with the tool. Finally, pull all the big root pieces that protrude from the ground. There will be some re-sprouting from this, but the reappearing ivy is quite manageable if you follow this simple program.
Experiments held in Kitsap County, Washington, have demonstrated that deep smother mulching (twelve to twenty-four inches deep) with coarse bark chips can reduce ivy stands by eighty percent in about three months. The remaining ivy can be hand-pulled easily after the mulch has softened the ground. These studies show that where it is possible to get large quantities of mulch in place, you do not need to remove any ivy ahead of time. Patches that were cut back before mulching were not killed off any better than the control patches that were just mulched without any precutting. The deep mulch is not harmful to the surrounding trees and can be removed for use in another area once the ivy has been cleaned up. After clearing and replanting, check up on the site two or three times a year, and remove any ivy that re-sprouts or reseeds.