Beneficial Landscaping - Invasive Plants
English Ivy, a Runaway Ornamental
From California to British Columbia (and elsewhere nationally), English ivy, known scientifically as Hedera helix, has been used for years as a popular ground cover and climbing vine. While there are plant societies dedicated to its virtues and varieties, without adequate control, English ivy can become invasive. This is particularly true in our urban natural areas such as greenbelts and remnant forest patches, although English ivy is now penetrating old growth forests. The vine is so invasive, in fact, that in February, the Oregon Noxious Weed Board voted unanimously to list English ivy as a noxious species in Oregon, where it joins the ranks of notorious weeds such as tansy ragwort, Himalayan blackberry, purple loosestrife, and Scotch broom. English ivy has been identified as an invasive species in at least 28 states.
Why is this? English ivy is an evergreen woody vine that spreads rapidly, can climb to a height of 30 meters and when mature, flowers prolifically. The vines, which can live to be hundreds of years old, produce berries that are eaten by birds, which disseminate the seeds. As a spreading ground cover, the plant forms an ivy monoculture or “desert” on the forest floor, overwhelming native ground covers and shrubs, and aggressively climbing trees. Trees are weakened when English ivy consumes the water and nutrients needed by the tree roots, and the tree trunks and branches enveloped by the vines are pulled down by the weight of the stems, leaf mass, and the additional wind and water they capture.
English ivy was once thought to be useful for erosion control. However, because landslides occur in ivy-covered settings, it is now recognized that its foliage overwhelms and prevents the growth of other plants that would hold the soil, and its shallow roots leave slopes vulnerable to erosion.
Control is also a challenge. English ivy grows well in sun and shade, can grow year round when deciduous plants are dormant, thrives in droughty and soggy soils, and its waxy leaves retain water and repel herbicides. Thus far, mechanical control seems to be most effective: sawing, clipping, and manual removal of the vines coupled with ongoing vigilance and maintenance.
The upshot is that, while English ivy is listed as a noxious weed in Oregon, it is not quarantined, nor is it listed in other northwestern states. It is still sold in nurseries, and can be used and enjoyed in a variety of settings. Efforts to landscape for environmental, economic, and aesthetic benefits, however, may require monitoring for English ivy (and other weedy) infestations, judicious control, and even removal. For advice about suitable substitutes, contact your local cooperative extension office, conservation district, university or other knowledgeable source. Top
Invasive Exotic Plants -- Trouble with a capital "T"
Invasive exotic plants (English ivy is one example) are non-native to the ecosystem. They have the ability to rapidly infest new areas and overwhelm existing vegetation, and are likely to cause economic harm or harm to human health or the environment. Invasive species are cause for alarm because they are
robbing us of our natural heritage. They are second only to habitat loss as the greatest contributor to decreasing global biodiversity. Invasive species also cost billions annually in damages to agriculture, recreation, tourism, and many other sectors.
So what can we do about this problem?
1. Learn about invasive plants, especially those that infest your area. The National Park Service has an excellent primer on invasives at www.nps.gov/plant/alien/bkgd.htm. Contact the local weed board or Cooperative Extension office to learn about the species of concern in your area.
2. Prevent infestations. Avoid or minimize clearing and disturbance of natural areas, including clearing of native vegetation. Plan to clear no more than you are willing and able to maintain. Land that is not replanted soon after clearing, will be invaded by weedy plants common to the area. For landscaping, site restoration, or erosion control, use plants that are native to your local region or those that are not known to be invasive.
3. Control outbreaks. Report new infestations of problem plants to land managers. Stop infestations on your own land before the problem becomes large. Seek the least environmentally damaging means for controlling infestations. The Urban Pesticide Education Strategy Team website at www.ecy.wa.gov/programs/wq/nonpoint/upest/index.htm offers integrated pest management information. Organize or volunteer to participate in weed control efforts in your community.
4. Restore native vegetation. Salvaging native plants from cleared areas and using native plants for landscaping will help to restore our natural heritage--and can bring you joy! Harmony comes with getting to know the native flora, enjoying the wildlife that come to live there, and restoring the integrity of our ecosystems.