English Ivy Facts, Uses and Problems
English ivy is a beautiful plant with a long history. Some people value ivy for its ability to form an attractive cover over walls and tree trunks. Other people consider the plant to be an annoying weed that damages the environment and must be eradicated.
English ivy is native to Europe, western Asia and northern Africa. The plant has been introduced to other parts of the world. Unfortunately, as an introduced plant ivy may have no natural enemies to control its growth and may become invasive. An "invasive" plant spreads rapidly and hurts native organisms.
Ivy is mildly poisonous. In addition, some people develop dermatitis after coming into contact with the plant. On the other hand, the plant may have health benefits. It has other benefits as well, even in North America, where it can be a problematic plant. In this article I'll discuss English ivy from a North American perspective.
The English Ivy Plant
English ivy, or Hedera helix, is an evergreen plant that is found in many parts of Canada and the United States. Hedera hibernica is a similar plant that has also been introduced to North America and is often known as English ivy. In its native habitat the common name of this plant is Atlantic or Irish ivy. Like Hedera helix, it may become invasive.
The part of English ivy that most people are familiar with is the thick, lobed and often glossy leaves. These are usually medium to dark green in color and have light green, yellow or white veins. There are three to five lobes on each leaf.
The leaves sometimes have an attractive variegated appearance consisting of two or more colors. These colors include dark green, light green, yellow, white and red. English ivy can be found in a cultivated form as well as a wild one. Cultivated variegated ivy is a popular addition to plant containers and landscaped areas.
English ivy stems with lobed leaves are actually the juvenile form of the plant. The adult flowering stems have oval leaves instead. Ivy has yellow-green flowers that are borne in clusters. The flowers are generally produced in the fall in the part of North America where I live. They produce blue-black berries that don't ripen until late winter or early spring.
How Does Ivy Attach to Surfaces?
English ivy is a climbing, trailing and creeping vine. It develops long stems that become thick and very strong as they mature. The plant can climb as high as ninety feet if it has a good support.
An ivy plant has two types of roots. The subterranean roots extend into the soil, attaching the plant to the ground and absorbing water and nutrients from the soil. Clumps of adventitious or aerial roots are located at intervals along the climbing stems. The function of these roots is to attach the plant to a surface as it climbs.
Until quite recently it was thought that the only factor joining the adventitious roots to the support was a glue produced by the roots. New research indicates that the glue is not the only factor involved. A root actually changes shape to anchor the plant. It also produces root hairs that fit into crevices in the support.
The English Heritage organization has published an interesting document assessing the effects of ivy on walls and monuments. Their research suggests that in some cases ivy causes no damage to walls but in other cases it does cause damage.
Does Ivy Damage Walls?
Ivy may or may not damage walls. The topic is a controversial one. Some people say that ivy is destructive, causing walls to crumble as it clings to them. Others say that ivy actually protects walls.
Ivy is often said to cause walls to break down as it sends its roots into crevices. However, some researchers say that instead of causing crumbling, ivy often attaches to sections of walls that are already starting to crumble and have many crevices that the roots can enter.
Supporters of English ivy say that ivy growing on the outside of a building helps a wall by providing thermal insulation, keeping it cooler in summer and warmer in winter. Some people claim that ivy traps water next to the wall, increasing structural damage, while others say that the waxy covering on ivy leaves repels water from the wall instead.
It can certainly be difficult to remove ivy from a wall once it's attached, since it clings to the wall so tightly. Bits of plaster may be removed with the ivy and pieces of root and ugly marks may be left behind.
English Ivy and the Environment
English ivy can spread rapidly and aggressively and can be troublesome if its growth isn't controlled. In North America it grows all year in some areas. It thrives in shade but also grows in sunny areas. It also tolerates a wide variety of soils.
Sometimes ivy is accused unfairly of crimes. For example, it doesn't damage tree trunks directly. It attaches to them with its adventitious roots, but these don't penetrate the trunk or absorb nutrients from the tree.
If there is a very dense growth of ivy it may damage trees indirectly. The ivy's weight may injure the tree. In addition, a sheet of ivy may act like a sail and make the tree more susceptible to damage caused by windstorms. The ivy may also block light that the tree and other plants need for photosynthesis. Photosynthesis is the process in which plants use light energy to produce their food. Ivy is also said to trap water that increases the chance of plant disease, although as in the case of ivy growing on walls not everyone agrees with this idea.
In the wild, the creeping form of ivy can prevent light from reaching seedlings, causing them to die. The ivy may also smother wild flowers and ferns. Some people appreciate English ivy as a ground cover in their garden, however.
Research suggests that English ivy can absorb particles that are polluting the air. English Heritage is one organization that has found evidence supporting this idea. They examined ivy growing beside very busy roads and discovered that it removed fine particles from the surrounding air. The organization says that they would like to do more research in order to determine whether their discovery is applicable to other areas.
Monarch Butterflies Feeding on English Ivy Nectar in California
English Ivy and Wildlife
English ivy does have benefits for the environment. It can be very helpful for wildlife in its native habitat. In Europe, the ivy on tree trunks provides a hiding place for a range of small mammals and a nesting site for birds. Unfortunately, in North America the "small mammals" that shelter in ivy seem to be mainly rats, especially the Norway rat, which is a pest. The nectar inside English ivy flowers is a food source for bees and butterflies in both Europe and North America. Some North American birds eat the berries. Far more European bird species feed on the berries, however.
How to Deal with an Ivy Invasion
How to Control or Remove English Ivy
The war against unwanted English ivy can be won with effort and persistence. The task involves cutting the ivy at frequent intervals (or all at once if the growth is small) and then digging out the roots. Protective gloves and clothing are useful, especially if a person develops dermatitis after touching ivy. Pruning shears, loppers or a saw are needed to cut the stems, depending on their thickness.
Experts often say that when trying to remove a large ivy vine, cuts should be made at shoulder height and at ankle height. This may enable the vine to be unravelled from a tree trunk. However, some people recommend that the upper portion of the vine be left to die naturally and crumble (as it will do, since it no longer has a water supply), because pulling the vine down may damage the tree. Experts also say that a wide zone around the base of the tree trunk should be cleared of ivy to prevent or delay a new invasion. Once the ground is clear it should be covered with mulch.
A gardener will likely need to return to an ivy patch in a garden periodically to do more cutting, but the process usually becomes easier as the ivy thins out. As soon as the soil can be reached, digging is necessary to remove the roots. It's important to realize that the plant can regrow from a piece of root or stem.
Once all the ivy seems to have been removed, the area should be checked periodically to ensure that new plants aren't growing. Ivy is much easier to deal with when its stems are thin and relatively weak than when they are thick and strong.
Invasive Ivy in Woodlands
Health Effects of English Ivy
Intact parts of the English ivy plant should never be eaten. The plant is considered to be mildly poisonous, but the dangers of plant ingestion increase with the amount eaten.
Ingestion of berries or leaf material in small quantities may cause no symptoms or only minor gastrointestinal upset. Ingesting large amounts of the plant can cause breathing difficulties, muscle weakness, coordination problems, fever, hallucinations and even coma.
A standardized extract made from the English ivy plant is generally safe, depending on how the extract is made. It may even be useful medicinally. A "standardized" extract is one with a known concentration of the active substance. This concentration is chosen for both effectiveness and safety.
It's advisable to wear protective gloves when handling English ivy. Ivy contains a substance called falcarinol that can cause dermatitis as well as blisters when people handle the ivy plant. Dermatitis is a condition in which the skin becomes inflamed, red and itchy. Both irritant contact dermatitis and allergic contact dermatitis can be caused by ivy contact. In irritant contact dermatitis, the skin is damaged by touching a substance. People with allergic contact dermatitis experience an allergic response after coming into contact with a substance that acts as an allergen. Interestingly, not everyone develops dermatitis after touching ivy.
In Europe, English ivy extracts are used as an expectorant. An expectorant is a substance that relieves coughs by thinning mucus, enabling it to be coughed up easily. Ivy extract is approved for use by the German Commission E. This organization is a scientific advisory group that examines the safety and effectiveness of traditional herbal remedies.
There is a some evidence that English Ivy extracts help the coughs that develop in certain health conditions, but ivy seems to work no better than other expectorants. Medicines containing guaifenesin are often used as equivalent expectorants in North America.
Ivy and Cancer in Mice
Potential Health Benefits of Ivy Chemicals
English ivy may have other health benefits for humans in addition to acting as an expectorant. Like other plants, ivy contains many different chemicals in a wide range of concentrations. Some of these chemicals may be helpful for us. Although the plant isn't currently used for either of the following applications, it may be in the future.
Falcarinol is found in carrots as well as English ivy. In carrots it acts as a natural pesticide that fights fungi. In one experiment, mice were fed freeze dried carrots containing falcarinol, corn starch to which an equivalent amount of falcarinol had been added or corn starch on its own. All of the mice in the experiment were given a chemical that causes colon cancer.
After the experimental treatments were finished, the researchers examined lesions (damaged areas) in the animal's colons that typically enlarge and become tumours. The lesions in the mice that received falcarinol were significantly smaller than those in the mice that didn't receive falcarinol. The researchers concluded that the falcarinol had delayed or slowed the development of cancer.
The mouse research is very interesting, but the discovery doesn't necessarily mean that falcarinol will have the same effect in humans. More research is needed.
The adhesive secreted by the root hairs of English ivy contain tiny nanoparticles that have been found to block dangerous ultraviolet radiation. They may be able to act as a safe human sunscreen. Nanoparticles of titanium dioxide and zinc oxide are already used in sunscreens. There is some concern that the nanoparticles of these chemicals can travel through our skin and into our body, however, where they may have harmful effects. English ivy nanoparticles may be safer, although this hasn't been proven yet.
Ivy Alternatives For Gardens
Growing English Ivy
English ivy is a beautiful plant. However, it's potentially harmful to the environment. Growing it deliberately requires caution. Landscapers and gardeners may love ivy, but its ability to grow invasively, hide pests and interfere with the growth of other plants needs to be taken seriously. A dense growth of ivy can affect not only the ivy grower's garden but also their neighborhood.
The history of English ivy in North America is a sad one, as it is for many introduced plants. Ivy is often referred to as a "noxious weed" instead of a valued part of its ecosystem. Some people may think that importing a plant from another part of the world either deliberately or accidentally is unimportant, but there may be serious consequences. Without the natural checks and balances that often develop during their long occupation in their native habitat, introduced plants may become invasive and damage their surroundings.
© 2014 Linda Crampton