Hedera helix

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Hedera helix (Common Ivy) is a species of ivy native to most of Europe. It is an evergreen climbing plant, growing to 20-30 m high where suitable sufaces (trees, cliffs, walls) are available, and also growing as ground cover where there are no vertical surfaces. It holds on to tree bark and rock by means of short adhesive rootlets.

The leaves are alternate, 4-8 cm long, with a 3-10 cm long petiole; they are of two types, with palmately five-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 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 closely related species Hedera hibernica is often treated as a variety or subspecies of H. helix, though they differ in chromosome number so do not hybridise readily. H. helix can be best distinguished by its usually smaller and slightly more deeply lobed leaves and somewhat less vigorous growth, though identification is often not easy.

Hedera helix has been introduced in North America, where, known as "English Ivy", it has become an invasive species.

References

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

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