Hedera helix, simply ivy, or common ivy, English ivy, European ivy, King's choice ivy, is a species of flowering plant in the family Araliaceae. It is native to most of Europe and parts of western Asia. Ivy is a clinging evergreen vine that grows on tree trunks, walls, and fences in gardens, waste spaces, and wild habitats. Ivy is common as an ornamental plant, but escaped plants become naturalised outside its native range. Ivy has considerable cultural significance and symbolism. Synonyms include Hedera acuta, Hedera arborea ('tree ivy'), Hedera baccifera, and Hedera grandifolia. Other common names are bindwood and lovestone.
Description Hedera helix is an evergreen climbing plant, growing to 20–30 m (66–98 ft) high where suitable surfaces (trees, cliffs, walls) are available, and also growing as groundcover where no vertical surfaces occur. It climbs by means of aerial rootlets with matted pads which cling strongly to the substrate. The ability to climb on surfaces varies with the plant's variety and other factors: H. helix prefers non-reflective, darker and rough surfaces with near-neutral pH. It generally thrives in a wide range of soil pH with 6.5 being ideal, prefers moist, shady locations and avoids exposure to direct sunlight, the latter promoting drying out in winter. The leaves are alternate, 50–100 mm (2–4 in) long, with a 15–20 mm (0.6–0.8 in) 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 from late summer until late autumn, individually small, in 3-to-5 cm-diameter (1.2-to-2.0 in) umbels, greenish-yellow, and very rich in nectar, an important late autumn food source for bees and other insects. The fruit are purple-black to orange-yellow berries 6–8 mm (0.2–0.3 in) in diameter, ripening in late winter, and are an important food source for many birds. One to five seeds are in each berry, which are dispersed after being eaten by birds.
Subspecies The three subspecies are:
H. h. helix − central, northern and western Europe, plants without rhizomes, purple-black ripe fruit, H. h. poetarum Nyman (syn. Hedera chrysocarpa Walsh) (Italian ivy, poet's ivy) − southeast Europe and southwest Asia (Italy, Balkans, Turkey), plants without rhizomes, orange-yellow ripe fruit, H. h. rhizomatifera McAllister − southeast Spain, plants rhizomatous, purple-black ripe fruit. The closely related species Hedera canariensis and Hedera hibernica are also often treated as subspecies of H. helix, though they differ in chromosome number and so do not hybridise readily. H. helix can be best distinguished by the shape and colour of its leaf trichomes, usually smaller and slightly more deeply lobed leaves and somewhat less vigorous growth, though identification is often not easy.
Etymology The genus name Hedera is the Classical Latin word for 'ivy', which is cognate with Greek χανδάνω (khandánō) 'to get, grasp', both deriving ultimately from Proto-Indo-European *gʰed(h)- 'to seize, grasp, take'. The specific epithet helix was borrowed into Latin from Ancient Greek ἕλιξ (helix), 'helix', 'spiral'.. The binomial in its entirety thus has the meaning "the clinging plant that coils in spirals (helices)".
Distribution and habitat
The range of Hedera helix is from Ireland northeast to southern Scandinavia, south to Portugal, and east to Ukraine, Iran and northern Turkey. In Britain, it is very common and widespread, but absent from the Isle of Man and Channel Islands. The northern and eastern limits are at about the −2 °C (28 °F) winter isotherm, while to the west and southwest, it is replaced by other species of ivy. Hedera helix itself is much more winter-hardy and survives temperatures of −23.3 °C (−9.9 °F) (USDA Zone 6a) and above.
Invasive species
Like other exotic species, ivy has predominantly been spread by human action. H. helix is labeled as an invasive species in parts of the world.
Australia The Centre for Invasive Species Solutions lists Hedera helix as a weed across southern, especially south-eastern Australia, and local councils provide advice on how to remove it and limited services for removal. It is officially scheduled as a weed in Western Australia and the Australian Capital Territory. Hedera helix is the only species of ivy bearing the legal status of 'declared weed' in Australia; however, it may be the case that much of what is identified as invasive "English Ivy" in Australia is in reality Hedera hibernica.
Canada Although common as a winter holiday decoration, H. helix is invasive and is a pathogen alternate host in British Columbia.
New Zealand H. helix has been listed as an "environmental weed" by the Department of Conservation since 1990.
United States In the United States, H. helix is considered weedy or invasive in a number of regions and is on the official noxious weed lists in Oregon and Washington, with its sale being banned in both states. Like other invasive vines such as kudzu, H. helix can grow to choke out other plants and create "ivy deserts". State- and county-sponsored efforts are encouraging the destruction of ivy in forests of the Pacific Northwest and the Southern United States. Ivy can easily escape from cultivated gardens and invade nearby parks, forests and other natural areas via squirrels and birds.
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