Trees & Shrubs – Climbing Plants – Ivy
Hedera, commonly called ivy (plural ivies), is a genus of 12–15 species of evergreen climbing or ground-creeping woody plants in the family Araliaceae, native to western, central and southern Europe, Macaronesia, northwestern Africa and across central-southern Asia east to Japan and Taiwan.
Hedera helix (common ivy, English ivy, European ivy, or just ivy) is the species native to Britain and most of Europe and western Asia. A rampant, clinging evergreen vine, it is a familiar sight in gardens, waste spaces, on house walls, tree trunks and in wild areas across its native habitat. It is labelled as an invasive species in a number of areas where it has been introduced.
On level ground they remain creeping, not exceeding 5–20 cm height, but on suitable surfaces for climbing, including trees, natural rock outcrops or man-made structures such as quarry rock faces or built masonry and wooden structures, they can climb to at least 30 m above the ground. Ivies 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 tops of rock faces, from 2 m or more above ground. The juvenile and adult shoots also differ, the former being slender, flexible and scrambling or climbing with small aerial roots to affix the shoot to the substrate (rock or tree bark), the latter thicker, self-supporting and without roots. The flowers are greenish-yellow with five small petals; they are produced in umbels in autumn to early winter and are very rich in nectar. The fruit is a greenish-black, dark purple or (rarely) yellow berry 5–10 mm diameter with one to five seeds, ripening in late winter to mid-spring. The seeds are dispersed by birds which eat the berries.
The species differ in detail of the leaf shape and size (particularly of the juvenile leaves) and in the structure of the leaf trichomes, and also in the size and, to a lesser extent, the colour of the flowers and fruit. The chromosome number also differs between species. The basic diploid number is 48, while some are tetraploid with 96, and others hexaploid with 144 and octaploid with 192 chromosomes.
Ivies are of major ecological importance for their nectar and fruit production, both produced at times of the year when few other nectar or fruit sources are available. The Ivy Bee Colletes hederae is completely dependent on ivy flowers, timing its entire life cycle around ivy flowering. The fruit are eaten by a range of birds, including thrushes, blackcaps, and woodpigeons. 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.
The following species are widely accepted; they are divided into two main groups, depending on whether they have scale-like or stellate trichomes on the undersides of the leaves:
- Trichomes scale-like
- Hedera algeriensis Hibberd – Algerian ivy. Algeria, Tunisia (Mediterranean coast).
- Hedera canariensis Willd. – Canaries ivy. Canary Islands.
- Hedera colchica (K.Koch) K.Koch – Persian ivy. Alborz, Caucasus, Turkey.
- Hedera cypria McAllister – Cyprus ivy (syn. H. pastuchovii subsp. cypria (McAll.) Hand). Cyprus (Troodos Mts.)
- Hedera iberica (McAllister) Ackerfield & J.Wen – Iberian ivy. SW Iberian coasts.
- Hedera maderensis – Madeiran ivy. Madeira.
- Hedera maroccana McAllister – Moroccan ivy. Morocco.
- Hedera nepalensis K.Koch – Himalayan ivy (syn. H. sinensis (Tobl.) Hand.-Mazz.). Himalaya, SW China.
- Hedera pastuchowii G.Woronow – Pastuchov’s ivy. Caucasus, Alborz.
- Hedera rhombea (Miq.) Siebold ex Bean – Japanese ivy. Japan, Korea, Taiwan.
- Trichomes stellate
- Hedera azorica Carrière – Azores ivy. Azores.
- Hedera helix L. – Common ivy (syn. H. caucasigena Pojark., H. taurica (Hibberd) Carrière). Europe, widespread.
- Hedera hibernica (G.Kirchn.) Bean – Atlantic ivy (syn. H. helix subsp. hibernica (G.Kirchn.) D.C.McClint.). Atlantic western Europe.
The species of ivy are largely allopatric and closely related, and many 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.
The only verified hybrid involving ivies is the intergeneric hybrid × Fatshedera lizei, a cross between Fatsia japonica and Hedera hibernica. This hybrid was produced once in a garden in France in 1910 and never successfully repeated, the hybrid being maintained in cultivation by vegetative propagation. Despite the close relationship between Hedera helix and H. hibernica (until relatively recently considered conspecific), no hybrids between them have yet been found. Hybridisation may however have played a part in the evolution of some species in the genus.
Uses & Cultivation
Ivies are very popular in London for their evergreen foliage, attracting wildlife, and for adaptable design uses in narrow planting spaces and on tall or wide walls for aesthetic addition, or to hide unsightly walls, fences and tree stumps. Numerous cultivars with variegated foliage and/or unusual leaf shapes have been selected for horticultural use.
Problems with Ivy on trees.
Much discussion has involved whether or not ivy climbing trees will harm them. In Europe the harm is generally not significant although there can be competition for soil nutrients, light, and water, and senescent trees supporting heavy ivy growth can be liable to wind-throw damage.
The berries are moderately toxic to humans, but are very bitter, so poisoning is rare. Ivy foliage contains triterpenoid saponins and falcarinol, a polyyne; falcarinol is capable of inducing an allergic reaction (contact dermatitis) in some people. People who have this allergy (strictly a Type IV hypersensitivity) are also likely to react to carrots and other members of the Apiaceae as they also contain falcarinol. It has also been shown to kill breast cancer cells.
Etymology and other names
The name ivy derives from Old English ifig, cognate with German Efeu, of unknown original meaning. The scientific name Hedera is the classical Latin name for the plant. Old regional common names in Britain, no longer used, include “Bindwood” and “Lovestone”, for the way it clings and grows over stones and bricks. US Pacific Coast regional common names for H. canariensis include “California ivy” and “Algerian ivy”; for H. helix, regional common names include the generic “English ivy”.
The name ivy has also been used as a common name for a number of other unrelated plants, including Boston ivy (Japanese Creeper Parthenocissus tricuspidata, in the family Vitaceae), Cape-ivy or German-ivy (Delairea odorata in the family Asteraceae), poison-ivy (Toxicodendron radicans in the family Anacardiaceae), and Swedish ivy (Whorled Plectranthus Plectranthus verticillatus, in the family Lamiaceae).
Ivy removal project
Ready for the growing season, watch this space for images as the ivy re-colonises the wall.