Ivy

Hedera (pronounced /ˈhɛdərə/;^[1] 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. Numerous hybrids and cultivars have been developed for specific aesthetic qualities and used in ornamental horticulture. On suitable surfaces, living tree, natural rock outcrop, or built masonry and lumber structures, they can climb from 3 feet (0.91 m) to at least 100 feet (30 m) above the ground.

Contents 1 Taxonomy and common names 2 Description 3 Uses and cultivation 4 Problems and dangers 4.1 Invasive exotic domination 4.2 On trees 4.3 On walls 4.4 Toxicity 5 Gallery 6 See also 7 References 8 External links

Taxonomy and common names

The species of ivy 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.

British regional common names for Ivies-H. spp. include 'Bindwood' and 'Lovestone,' for the way it clings and grows over stones and bricks. U.S. Pacific Coast regional common names for H. canariensis include 'California Ivy' and 'Algerian Ivy,' and for H. helix the generic 'English Ivy.'

True ivy can be confused visually and by common name with Boston Ivy and Virginia creeper (Parthenocissus spp.), which are climbers that grow on and up walls and buildings, but are deciduous and in the grape family. Another similar common name is Swedish Ivy (Plectranthus verticillatus), a common houseplant from Africa. Its name also can be confused with German ivy (Delairea odorata), in the sunflower family which is a serious invasive exotic in California, Hawaii, Oregon, New Zealand and Australia.

Description

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 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 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.

Uses and cultivation

Ivies are very popular in cultivation within their native range and compatible climates, for their evergreen foliage and cultivars with variegated foliage and/or unusual leaf shapes, attracting native wildlife, and adaptable design uses in narrow planting spaces and on tall-wide walls for aesthetic addition or 'problems coverage.' Frank Lloyd Wright is attributed with saying; "Doctors bury their mistakes, Architects cover them with ivy."

Ivy and vines are living, growing, and moving organisms that attach by twining, aerial roots, and/or tendrils to other plants or static surfaces and objects. On a building, this can result in displacement of building parts, materials or surfaces. When climbing by twining around objects, the diameter of the vine's stems or trunks increase with maturity. This can constrict another plant, often the host, sometimes killing it, or damage objects, or otherwise just create an attractive and living sculpture.^[2]

Problems and dangers

Invasive exotic domination

Several Ivy species have become a serious invasive species (invasive exotic) in natural native plant habitats, (especially riparian and woodland) types, and also a horticultural weed in gardens of the Western and Southern regions of the United States and Canada with milder winters. Ivy (Hedera spp.), being an introduced plant in North America, is without the natural pests and diseases that control its vigor in its native continents. Ivy creates a dense, vigorously smothering, shade-tolerant evergreen ground-cover here, positive characteristics in its horticultural use, that can spread through assertive underground rhizomes and above-ground runners quickly over large natural plant community areas and outcompete the native vegetation. Their ornamental horticulture use in California and other states is now discouraged or banned in certain jurisdictions and habitat adjacencies.^[3] Similar problems exist in Australia. For example, in both countries the North African drought-tolerant 'Algerian or California Ivy' (H. canariensis or H. algeriensis) and European 'English Ivy' (H. helix) were originally cultivated in garden, park, and highway landscaping, but have become aggressively invasive in coastal forests and riparian ecosystems now neccesitating costly eradication programs.^[4]

On trees

Much discussion has involved whether or not Ivy climbing garden trees will harm them. In Europe the opinion is that the harm is 'insignificant' although there can be competition for soil nutrients and water, and trees supporting heavy Ivy growth can be liable to windthrow damage. However harm and problems are significant in North America, where a tree's photosynthesis or structural strength can be overwhelmed by aggressive ivy growth leading to death directly or by opportunistic disease and insect attacks caused by weakness from the duress.

On walls

Concerns exist about damages by aerial roots and trunk growth to dry stacked stone, brick or stone and mortar, and stucco-plastered walls. Dry stacked stonework, over enough time for Ivy trunks to gain significant caliper, can be damaged or destroyed without ongoing training. For brick or stone and mortar construction it is of general opinion that a soundly mortared installation is impenetrable to the climbing runners' and thus not damaged, and even protected from weathering by the ivy deflecting rain impact off the mortar. However, walls with preexisting weakened or loose mortar may be badly damaged, as the ivy's roots penetrate the mortar and break up the wall. Subsequent ivy removal can be difficult, and often causes further damage. Modern mortars containing Portland cement and little lime are stronger than older mortar mixes composed of just sand and lime. Most mortar mixes began containing Portland Cement in the 1930s. Older mortar mixes are still used for laying softer types of bricks. Stucco and plaster walls are, at the least, aesthetically ruined after ivy pruning or removal, requiring a new topcoat or repainting, and sometimes needing restoration for structural and waterproofing problems. When ivy climbs on wooden structures and fences, there can be direct and secondary problems. The direct issues are runners and trunks growing between boards and expanding construction joints, thus destabilizing or destroying the structure. The secondary issues involve the entry of aerial roots into the lumber's grain causing the wood to split and allowing moisture and fungus to penetrate and accelerate wet rot and eventual collapse.

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). It has also been shown to kill breast cancer cells.^[5]

Gallery

A tree covered by ivy at Monticello	Tempelherrenhaus Weimar	Hedera helix berries	Ivy growing on a brick wall	Hedera colchica flowers	Hedera colchica foliage
Hedera hibernica with berries	Hedera helix leaves	Ivy vines.	Variegated Ivy	Removing invasive English ivy in the Pacific Northwest

See also

• Parthenocissus tricuspidata - Boston Ivy.
• Toxicodendron radicans - Poison Ivy.
• Delairea odorata - German Ivy or Cape Ivy.
• Plectranthus verticillatus - Swedish Ivy.
• List of air-filtering plants

References

Bibliography

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

Notes

External links

• Media related to Hedera at Wikimedia Commons