Ivy

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(Redirected from English ivy)

For other uses, see Ivy (disambiguation). "Hedera" redirects here. In typography, it is the name of a horticultural dingbat shaped like an ivy leaf.

{{Taxobox | color = lightgreen | name = Hedera | image = Hedera_hibernica1.jpg | image_width = 240px | image_caption = Hedera hibernica shoot with flower buds | regnum = Plantae | divisio = Magnoliophyta | classis = Magnoliopsida | ordo = Apiales | familia = Araliaceae | genus = Hedera | genus_authority = L. | subdivision_ranks = Species | subdivision = See text. }}

Hedera (English name ivy (plural, ivies) is a genus of about ten 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.

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

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Species

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 USSR, but are not regarded as distinct by most botanists.

Hedera algeriensis – Algerian ivy. Northwest Africa.
Hedera azorica – Azores ivy. Azores.
Hedera canariensis – Canaries ivy. Canary Islands.
Hedera colchica – Caucasian ivy or Persian ivy. Northern Turkey to Iran.
Hedera helix – Common or English ivy. Western & central Europe, except for the Atlantic coasts.
Hedera hibernica – Irish ivy. Atlantic coastal areas of Europe from Scotland & Ireland to Portugal.
Hedera maderensis – Madeiran ivy. Madeira.
Hedera nepalensis – Himalayan ivy. Himalaya, China, Taiwan.
Hedera pastuchowii – Pastuchov's ivy. Central Asia (southern states of the former USSR).
Hedera rhombea – Japanese ivy. Japan, Korea, China, Taiwan.

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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 (photo, right) 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.

Much has been argued as to whether ivy climbing trees will harm the tree or not; 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.

Hedera helix leaves	Hedera helix berries	Hedera hibernica fruit	Hedera colchica flowers
Hedera colchica foliage	Variegated Ivy	Tempelherrenhaus Weimar	An ivy-covered apartment house.