Hedera helix, the common ivy, European ivy, King's Choice ivy, or just ivy, is a species of flowering plant in the family Araliaceae. It is native plant 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 popular as an ornamental plant, but escaped plants have become naturalised outside its native range. Ivy has considerable cultural significance and symbolism.
Synonyms include Hedera acuta, Hedera arborea ('tree ivy'),[Bean, W. J. (1978) Trees and Shrubs Hardy in the British Isles Volume 2.] Hedera baccifera, and Hedera grandifolia.[International Plant Names Index] Other common names are bindwood and lovestone.
Description
Hedera helix is an
evergreen climbing plant, growing to high where suitable surfaces (
,
,
) are available, and also growing as
groundcover where no vertical surfaces occur. It climbs by means of
with matted pads which cling strongly to the substrate. The ability to climb on surfaces varies with the plants 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, long, with a petiole; they are of two types, with leaf shape 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 are produced from late summer until late autumn, individually small, 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 in diameter, ripening in late winter,
One to five are in each berry, which are dispersed after being eaten by birds.
Subspecies
The three
subspecies are:
-
H. h. helix
-
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 rhizome, purple-black ripe fruit.
The closely related species Hedera canariensis and Hedera hibernica are also often treated as subspecies of H. helix,[ The Holly and the Ivy. Shropshire Botanical Society Newsletter Autumn 2000: page 14]
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 *
'to seize, grasp, take'. The specific epithet
helix derives from
Ancient Greek ἕλιξ (helix), '
helix', and from the Latin helicem, 'spiral', first used around 1600. The binomial in its entirety thus has the meaning "the clinging plant that coils in spirals (helices)".
The modern English ivy derives from Middle English ivi, from Old English īfiġ, deriving in turn from Proto-Germanic *ibahs. The meaning is uncertain, but the word may be cognate with the Ancient Greek ἴφυον (íphuon), referring to not Hedera helix, but the unrelated English lavender, or Lavandula angustifolia.
Distribution and habitat
The range of European ivy is from
Ireland northeast to southern
Scandinavia, south to
Portugal, and east to
Ukraine and
Iran and northern
Turkey. In Britain, it is very common and widespread, but absent from the Isle of Man and
Channel Islands.
[Poland J, Clement EJ. 2020. The Vegetative Key to the British Flora. John Poland, Southampton, Second Edition. ]
The northern and eastern limits are at about the winter isotherm, while to the west and southwest, it is replaced by other species of ivy.[ Flora of NW Europe][Ackerfield, J. & Wen, J. (2002). A morphometric analysis of Hedera L. (the ivy genus, Araliaceae) and its taxonomic implications. Adansonia sér. 3, 24 (2): 197-212.][ Flora Europaea: Hedera helix][Stace, C. A. & Thompson, H. (1997). New Flora of the British Isles. Cambridge University Press ] Hedera helix itself is much more winter-hardy and survives temperatures of (Hardiness 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.
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 popular 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.
[ USDA Plants Profile: Hedera helix]
In the state of
Oregon, its sale or import is banned.
[ Oregon bans sale of English ivy, butterfly bushes][ Controlling English Ivy . Northwest Coalition for Alternatives to Pesticides.] 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.
[ Controlling English Ivy Arlington County, Virginia Department of Parks, Recreation and Community Resources.] Ivy can easily escape from cultivated gardens and invade nearby parks, forests and other natural areas via squirrels and birds.
Control and eradication
Once ivy is established it is very difficult to control or eradicate. If left untreated it will crowd out other ground cover plants and can choke out and kill shrubs and overstory trees.
Tested and successful methods of control are mechanical removal and chemical applications.
Damage to trees
Ivy can climb into the canopy of young or small trees in such density that the trees fall over from the weight,
a problem that does not normally occur in its native range.
In its mature form, dense ivy can destroy habitat for native wildlife and creates large sections of solid ivy where no other plants can develop.
It is also thought to be a reservoir for leaf scorch bacteria.
However, the UK Woodland Trust considers that it does not damage trees and hence does not require removal.
The ivy also blocks the sun from the trees that need it for photosynthesis.
Cultivation
Ivy is widely cultivated as an
ornamental plant. Within its native range, the species is greatly valued for attracting wildlife. The flowers are visited by over 70 species of nectar-feeding insects, and the berries eaten by at least 16 species of birds. The foliage provides dense evergreen shelter, and is also browsed by deer.
[ Plant for Wildlife: Common Ivy (Hedera helix) ]
In Europe, it is frequently planted to cover walls
However, ivy can be problematic. It is a fast-growing, self-clinging climber that is capable of causing damage to brickwork, guttering, etc., and hiding potentially serious structural faults, as well as harbouring unwelcome pests. Careful planning and placement are essential.
Cultivars
Over 30
have been selected for leaf traits such as yellow, white,
variegation (e.g. 'Glacier'), and deeply lobed (e.g. 'Sagittifolia'), and other traits like purple stems and slow,
dwarfing growth.
[ NCCPG Plant Heritage: The common ivy]
The following 16 cultivars have gained the Royal Horticultural Society's Award of Garden Merit:
-
'Angularis Aurea'
-
'Buttercup'
-
'Caecilia'
-
'Ceridwen'
-
'Congesta'
-
'Duckfoot'
-
'Glacier'
-
'Goldchild'
-
'Golden Ingot'
-
'Maple Leaf'
-
'Manda's Crested'
-
'Midas Touch'
-
'Parsley Crested'
-
'Shamrock'
-
'Spetchley'
-
'White Knight'
Toxicity and medical uses
Ivy berries are somewhat poisonous to humans, but extracts from ivy leaves are part of current
Cough Medicine.
[European Medicines Agency, Committee on Herbal Medicinal Products (2017). Assessment report on Hedera helix L., folium, pp. 5-16] A 2020 evidence review found that
H. helix preparations "may be a therapeutic option for treating early symptoms of respiratory tract infections", saying that "the best effectiveness for
H. helix preparations has been proven for coughing, as an expectorant and to reduce the frequency and intensity of cough. Only weak evidence was found for all other researched symptoms."
In the past, the leaves and berries were taken orally as an expectorant to treat cough and bronchitis.[Bown. D. (1995). Encyclopaedia of Herbs and their Uses. Dorling Kindersley, London. ] In 1597, the British herbalist John Gerard recommended water infused with ivy leaves as a wash for sore or watering eyes.
Previous studies showed that the H. helix
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Owing to the large number of in the leaves and fruits of H. helix, it is mildly poisonous to animals like rabbits and can lead to anemia.
In a hunting session for resources, birds would restrict the number of ivy berries ingested because of the moderate toxicity. However, berries are taken in larger quantities in the spring once they have ripened and lost some of their toxicity.
Use as building facade green
As with any self-climbing façade green, some care is required to make best use of the positive effects: Ivy
green wall of an old green wall is a familiar and often attractive sight. It has insulating as well as weather protection benefits, dries the soil and prevents wet walls, but can be problematic if not managed correctly.
Hedera helix grows vigorously and clings by means of fibrous roots, which develop along the entire length of the stems. These are difficult to remove, leaving an unsightly "footprint" on walls, and possibly resulting in expensive resurfacing work. Additionally, ivy can quickly invade Rain gutter and roof spaces, lifting tiles and causing blockages. It also harbors mice and other creatures. The plants have to be cut off at the base, and the stumps dug out or killed to prevent regrowth.
Mechanism of attachment
Hedera helix is able to climb relatively smooth vertical surfaces, creating a strong, long lasting adhesion with a force of around 300 nN.
This is accomplished through a complex method of attachment starting as adventitious roots growing along the stem make contact with the surface and extend root hairs that range from 20 to 400 μm in length. These tiny hairs grow into any small crevices available, secrete glue-like
, and
lignification. As they dry out, the hairs shrink and curl, effectively pulling the root closer to the surface.
The glue-like substance is a nano composite adhesive that consists of uniform spherical nanoparticles 50–80 nm in diameter in a liquid polymer matrix. Chemical analyses of the nanoparticles detected only trace amounts of metals, once thought to be responsible for their high strength, indicating that they are largely organic. Recent work has shown that the nanoparticles are likely composed in large part of arabinogalactan proteins (AGPs), which exist in other plant adhesives as well.
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