ivy

ivy, name applied loosely to any trailing or climbing plant, particularly cultivated forms, but more popularly a designation for Hedera helix, the so-called English ivy, and some related species of the family Araliaceae (ginseng family). Native to Europe and temperate Asia, English ivy is a woody evergreen vine, usually sterile, whose berries contain the poisonous principle hederin. Grown in numerous varieties, it is the most popular house and wall vine. The Boston, or Japanese, ivy (Parthenocissus tricuspidata, of Japan and China) and the American ivy, or Virginia creeper (P. quinquefolia, of North America), are similar species of the family Vitaceae (grape family). Both are sometimes called ampelopsis, a name usually reserved for another related genus. Kenilworth ivy, Cymbalaria muralis, of the family Scrophulariaceae (figwort family) is common to old ruins in Europe; it is often cultivated as a ground cover. Ivy was sacred to Bacchus and was associated with various pagan religions. It was formerly hung as a tavern sign in England. Ivy is classified in the division Magnoliophyta, class Magnoliopsida. The ginseng family ivies are in the order Umbellales, the grape family ivies in the order Rhamnales, and the figwort family ivies in the order Scrophulariales.

Either of two North American species of white-fruited woody vines or shrubs of the sumac, or cashew, family. The species found in eastern North America (Toxicodendron radicans) is abundant; a western species, known as poison oak, is less common. Both species are sometimes classified as genus Rhus. A key identifier is leaves with three mitten-shaped leaflets. Contact with urushiol, an oil produced by the plant, can cause severe inflammation and blistering of human skin. Urushiol may be carried from the plant on clothing, shoes, tools, or soil; by animals; or by smoke from burning plants. Because urushiol is nonvolatile, a reaction may result from wearing clothing a year or more after its contact with the plant.

Learn more about poison ivy with a free trial on Britannica.com.

Any of about five species of evergreen woody vines (rarely shrubs) that make up the genus Hedera in the ginseng family, commonly grown as ground covers and on stone walls, especially English ivy (H. helix), which climbs by aerial roots with adhering disks that develop on the stems. The tough, dark-green leaves of English ivy have three to five lobes and tend to droop horizontally from the stem. Unrelated plants called ivies include Boston ivy (Parthenocissus, or Ampelopsis, tricuspidata), a clinging woody vine in the grape family whose leaves turn bright scarlet in autumn, and poison ivy.

Learn more about ivy with a free trial on Britannica.com.

(born June 5, 1884, Pinner, Middlesex, Eng.—died Aug. 27, 1969, London) British novelist. She graduated from the University of London and published her first novel, Dolores, in 1911. Her second, Pastors and Masters (1925), introduced the style—employing clipped, precise dialogue to reveal her characters and advance the plot—that made her name. Her novels often dealt with struggles for power: Men and Wives (1931) featured a tyrannical mother, A House and Its Head (1935) a tyrannical father. She was created Dame of the British Empire in 1967.

Learn more about Compton-Burnett, Dame Ivy with a free trial on Britannica.com.

(born June 5, 1884, Pinner, Middlesex, Eng.—died Aug. 27, 1969, London) British novelist. She graduated from the University of London and published her first novel, Dolores, in 1911. Her second, Pastors and Masters (1925), introduced the style—employing clipped, precise dialogue to reveal her characters and advance the plot—that made her name. Her novels often dealt with struggles for power: Men and Wives (1931) featured a tyrannical mother, A House and Its Head (1935) a tyrannical father. She was created Dame of the British Empire in 1967.

Learn more about Compton-Burnett, Dame Ivy with a free trial on Britannica.com.

Hedera (English name ivy, plural ivies) is a genus of 15 species of climbing or ground-creeping evergreen woody plants in the family Araliaceae, native to the Atlantic Islands, western, central and southern Europe, northwestern Africa and across central-southern Asia east to Japan. On suitable surfaces (trees and rock faces), they are able to climb to at least 25–30 metres above the basal ground level.

They have two leaf types, with palmately lobed juvenile leaves on creeping and climbing stems, and unlobed cordate adult leaves on fertile flowering stems exposed to full sun, usually high in the crowns of trees or the top of rock faces. The juvenile and adult shoots also differ, the former being slender, flexible and scrambling or climbing with small roots to affix the shoot to the substrate (rock or tree bark), the latter thicker, self-supporting, and without roots. The flowers are produced in late autumn, individually small, in 3–5 cm diameter umbels, greenish-yellow, and very rich in nectar, an important late food source for bees and other insects; the fruit are small black berries ripening in late winter, and are an important food for many birds, though poisonous to humans. The seeds are dispersed by birds eating the fruit. The leaves are eaten by the larvae of some species of Lepidoptera such as Angle Shades, Lesser Broad-bordered Yellow Underwing, Scalloped Hazel, Small Angle Shades, Small Dusty Wave (which feeds exclusively on ivy), Swallow-tailed Moth and Willow Beauty.

Taxonomic note

The species are largely allopatric and closely related, and all have on occasion been treated as varieties or subspecies of H. helix, the first species described. Several additional species have been described in the southern parts of the former Soviet Union, but are not regarded as distinct by most botanists.

Uses and cultivation

Ivies are very popular in cultivation within their native range, both for attracting wildlife, and for their evergreen foliage; many cultivars with variegated foliage and/or unusual leaf shape have been selected. They are particularly valuable for covering unsightly walls.

Ivies have however proved to be a serious invasive weed in the parts of North America where winters are not severe, and their cultivation there is now discouraged in many areas. Similar problems exist in Australia where the plant was originally cultivated in gardens. For example, in the coastal basins of California drought-tolerant Algerian ivy (H. algeriensis or H. canariensis) has been planted as a ground cover around buildings and highways, but it has become an invasive weed in coastal forests, and riparian areas.

Much has been argued as to whether or not an ivy climbing a tree will cause harm to it; the consensus in Europe is that they do not harm trees significantly, though they may compete for ground nutrients and water to a small extent, and trees with a heavy growth of ivy can be more liable to windthrow. Problems are greater in North America, where trees may be overwhelmed by the ivy to the extent they are killed; this could be because ivy in North America, being introduced, is without the natural pests and diseases that control its vigour in its native areas. A more serious problem is that ivy creates a vigorous, dense, shade-tolerant evergreen groundcover (precisely the characteristics for which it is often cultivated) that can spread over large areas and outcompete native vegetation.

Similar concerns are expressed about damage to walls. It is generally considered that a soundly mortared wall is impenetrable to the climbing roots of ivy and will not be damaged, and is also protected from further weathering by the ivy keeping rain off the mortar. Walls with already weak or loose mortar may however be badly damaged, as the ivy is able to root into the weak mortar and further break up the wall. Subsequent removal of the ivy can be difficult, and is likely to cause more damage than the ivy itself. Modern mortars that contain portland cement and little lime are stronger than older mortar mixes that were largely composed of just sand and lime. Most mortar mixes changed to contain Portland cement in the 1930s. Soft mortar is still used when laying softer brick. If ivy is allowed to climb wooden structures, then the aerial roots are likely to enter into the wood grain causing the wood to split, allowing moisture and fungus to penetrate the wood and accelerating wet rot.

Regional English names for ivy include Bindwood and Lovestone (for the way it clings and grows over stones and brickwork).

Toxicity

Although far less toxic than poison ivy, which is unrelated to this genus, ivy contains triterpenoid saponins and falcarinol, a polyyne. Falcarinol is capable of inducing an allergic reaction (contact dermatitis), although it has been shown to kill breast cancer cells as well.

Gallery

See also

• Poison ivy - unrelated to this genus
• Boston ivy - also cultivated and may grow up walls
• List of air-filtering plants

References

• McAllister, H. (1982). New work on ivies. Int. Dendrol. Soc. Yearbook 1981: 106-109.