Ivy is a term given to a vine that creeps--typically the English Ivy, but also poison ivy and other types, such as Devil's Ivy and Swedish Ivy. This information relates specifically to English ivy, or Hedera as it is termed in Latin. In some states this ivy is such a successful grower that it has become obnoxious, crowding out other native plants and therefore now listed as invasive. In other states, people still plant it as a ground cover for areas where erosion is a problem.
English ivy is an easy plant to grow and gardeners can train it to form a topiary. According to the USDA, ivy is present in 32 of the 50 states in the U.S., and is present in Canada. Since it is a perennial, you do not have to replant it every year. It is very cold-hardy. It resists fire, stays evergreen year-round and has no known toxicities. English Ivy tolerates shade and is easily propagated.
English ivy attracts some concern since it has the ability to grow in shade and therefore in forests. It will climb up trees, wrapping around branches until the weight of it pulls the branches down. It grows so thickly along the forest floor that it will choke out new tree seedlings. In areas where the tree stands are very old, such as the redwood forests, the concern is that the vines will crowd out the new trees and destroy the old ones.
The process of removing English Ivy from forests involves cutting the vines that are going up the tree at eye level, leaving the vines in the trees to die. Workers pull the lower portions by hand or with a McLeod rake, rolling it back like a carpet. They come back the next growing season to make sure no new sprouts have come up, and if so, they remove them by hand-pulling.
English ivy can be propagated most easily by pulling up a section that has rooted itself. Cut the stem on the other side of the roots. Place the section into the soil deep enough so that the roots are covered. Water well.
Cuttings without roots can also be coaxed into producing roots, simply by trimming off the lower leaves and burying the stem in damp soil or a cup of water. Once the roots have grown an inch or more, the cuttings can be planted in a permanent spot.
Many old stone or brick buildings on the east coast of the United States have ivy covering their walls. This ivy actually serves a protective covering, protecting the brick from the elements. The plants do not work into the mortar of the buildings; rather they secrete their own form of "cement" that securely holds the ivy on the walls.