Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Datasheet

Hedera helix
(ivy)

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Datasheet

Hedera helix (ivy)

Summary

  • Last modified
  • 27 September 2018
  • Datasheet Type(s)
  • Invasive Species
  • Pest
  • Host Plant
  • Preferred Scientific Name
  • Hedera helix
  • Preferred Common Name
  • ivy
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Plantae
  •     Phylum: Spermatophyta
  •       Subphylum: Angiospermae
  •         Class: Dicotyledonae
  • Summary of Invasiveness
  • H. helix is an important horticultural woody climber from Europe introduced to many other temperate zones and it is now spreading in many regions. Seeds of this toxic plant are readily dispersed by birds. Once established it spreads vegetatively on t...

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Pictures

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PictureTitleCaptionCopyright
Hedera helix (ivy); habit, showing foliage. Forsyth County, Clemmons, North Carolina, USA. August 2018.
TitleHabit
CaptionHedera helix (ivy); habit, showing foliage. Forsyth County, Clemmons, North Carolina, USA. August 2018.
Copyright©Darren Tayloe-2018
Hedera helix (ivy); habit, showing foliage. Forsyth County, Clemmons, North Carolina, USA. August 2018.
HabitHedera helix (ivy); habit, showing foliage. Forsyth County, Clemmons, North Carolina, USA. August 2018.©Darren Tayloe-2018
Hedera helix (ivy); complete ground cover with lobed leaves.
TitleHabit
CaptionHedera helix (ivy); complete ground cover with lobed leaves.
Copyright©Pierre Binggeli
Hedera helix (ivy); complete ground cover with lobed leaves.
HabitHedera helix (ivy); complete ground cover with lobed leaves.©Pierre Binggeli
Hedera helix (ivy); typical growth of ivy on both the ground and on deciduous trees. Note canopies with various degrees of infestation.
TitleHabit
CaptionHedera helix (ivy); typical growth of ivy on both the ground and on deciduous trees. Note canopies with various degrees of infestation.
Copyright©Pierre Binggeli
Hedera helix (ivy); typical growth of ivy on both the ground and on deciduous trees. Note canopies with various degrees of infestation.
HabitHedera helix (ivy); typical growth of ivy on both the ground and on deciduous trees. Note canopies with various degrees of infestation.©Pierre Binggeli
Hedera helix (ivy); large deciduous trees with trunks covered by ivy.
TitleHabit
CaptionHedera helix (ivy); large deciduous trees with trunks covered by ivy.
Copyright©Pierre Binggeli
Hedera helix (ivy); large deciduous trees with trunks covered by ivy.
HabitHedera helix (ivy); large deciduous trees with trunks covered by ivy.©Pierre Binggeli
Hedera helix (ivy); large coastal plant with a stout trunk (ca.10cm diameter) growing over a small cliff.
TitleHabit
CaptionHedera helix (ivy); large coastal plant with a stout trunk (ca.10cm diameter) growing over a small cliff.
Copyright©Pierre Binggeli
Hedera helix (ivy); large coastal plant with a stout trunk (ca.10cm diameter) growing over a small cliff.
HabitHedera helix (ivy); large coastal plant with a stout trunk (ca.10cm diameter) growing over a small cliff.©Pierre Binggeli
Hedera helix (ivy); fully grown but immature fruits and immature fruits with simple leaves.
TitleImmature fruits
CaptionHedera helix (ivy); fully grown but immature fruits and immature fruits with simple leaves.
Copyright©Pierre Binggeli
Hedera helix (ivy); fully grown but immature fruits and immature fruits with simple leaves.
Immature fruitsHedera helix (ivy); fully grown but immature fruits and immature fruits with simple leaves.©Pierre Binggeli
Hedera helix (ivy); flower buds, flowers and young fruits.
TitleFlower buds
CaptionHedera helix (ivy); flower buds, flowers and young fruits.
Copyright©Pierre Binggeli
Hedera helix (ivy); flower buds, flowers and young fruits.
Flower budsHedera helix (ivy); flower buds, flowers and young fruits.©Pierre Binggeli
Hedera helix (ivy); rootlets on main stem.
TitleRootlets
CaptionHedera helix (ivy); rootlets on main stem.
Copyright©Pierre Binggeli
Hedera helix (ivy); rootlets on main stem.
RootletsHedera helix (ivy); rootlets on main stem.©Pierre Binggeli

Identity

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Preferred Scientific Name

  • Hedera helix L.

Preferred Common Name

  • ivy

Other Scientific Names

  • Hedera hibernica Carr.

International Common Names

  • English: Atlantic ivy; common ivy; English ivy
  • Spanish: hiedra; yedra comun
  • French: Bourreau des arbres; Herbe de St Jean; lierre; lierre commun
  • Portuguese: hera

Local Common Names

  • Finland: köynneliäs muratti
  • Germany: Efeu; Gemeiner Efeu
  • Italy: edera
  • Netherlands: klimop
  • Sweden: murgroena; murgröna

EPPO code

  • HEEHE (Hedera helix)
  • HEEHI (Hedera hibernica)

Summary of Invasiveness

Top of page H. helix is an important horticultural woody climber from Europe introduced to many other temperate zones and it is now spreading in many regions. Seeds of this toxic plant are readily dispersed by birds. Once established it spreads vegetatively on the forest floor and then climbs trees up to the canopy where it flowers and fruits freely. It reduces native plant diversity and associated fauna, threatens endangered species and alters nutrient dynamics of forest soils. It is difficult to control particularly in view of the ineffectiveness of herbicide sprayed on the foliage.

Taxonomic Tree

Top of page
  • Domain: Eukaryota
  •     Kingdom: Plantae
  •         Phylum: Spermatophyta
  •             Subphylum: Angiospermae
  •                 Class: Dicotyledonae
  •                     Order: Araliales
  •                         Family: Araliaceae
  •                             Genus: Hedera
  •                                 Species: Hedera helix

Notes on Taxonomy and Nomenclature

Top of page The genus Hedera is a complex group that has only been recently been clarified (Ackerfield and Wen, 2002) with 16 taxa (12 species) now recognized. Ackerfield and Wen (2002) provide a key to the identification of species and sub-species of Hedera based on trichome and leaf morphologies (see also Ackerfield, 2001). On the basis of differences in trichome positioning, leaf shape and chromosome number, McAllister (1990) recognised H. hibernica as a distinct species from H. helix. Tutin et al. (1968) have suggested that this taxon had originated from south-west Ireland. However, H. hibernica has still often been treated as H. helix subsp. hibernica (e.g. Stace, 1997). There are many forms and cultivars, for instance Brickell (1999) lists 28 cultivars/varieties of H. helix and four of H. hibernica. As both the taxonomic status and the extent of planting of the Hedera material introduced around the world is often not clear or even unknown, Hedera helix L. and Hedera hibernica Carr. are treated in this datasheet as one species complex, H. helix. Indeed, in the horticultural trade in the USA, the two species are commonly known as 'English ivy'. However, it is probable that H. helix and its various cultivars is the more common of the two taxa, especially as many more cultivars of H. helix are available on the market (Pennisi et al., 2001). No attempt has been made to differentiate between the two taxa in the distribution table. Indeed the introduced material may even consist of other Hedera taxa including some that were only recognized as subspecies until recently. For instance, Press and Short (1994) in their flora of Madeira, reported H. maderensis as H. helix subsp. canariensis. Although all Hedera species are commonly known as ivy, H. helix is often known as the common ivy or more specifically, the English ivy, whereas H. hibernica is known specifically as the Atlantic ivy, due to its limited, coastal distribution.

Description

Top of page H. helix is an evergreen woody perennial exhibiting marked morphological changes between its sterile and reproductive phases. The stem is long, either creeping or climbing and may attain a length of up to 30 m. It can be extremely long-lived and may reach an age of over 400 years. When old, stems may reach a diameter of over 10 cm and even produce a short trunk. The stem is attached to the substrate by numerous small roots produced at each leaf node, which bear vascular-arbuscular mycorrhiza. The deep green, glossy, leathery leaves are evergreen, heterophyllous, and mostly palmately lobed on sterile stems whereas those on flowering stems are ovate and larger. Leaves of H. helix are usually less than 8 cm across whereas those of H. hibernica are greater than 8 cm wide and have petioles half as long as the leaf blade. Leaves are long-lived and have a strong smell when crushed. The perfect, sometimes protandrous, yellow-green flowers, 5-7 mm across, are clustered on terminal inflorescences born on stems climbing to canopy height. The fruit, a drupe 6-9 mm in diameter, is green turning dark purplish/black when mature and contains 2-5 seeds (Grime et al., 1988; Stace, 1997; Reichard, 2000).

Plant Type

Top of page Perennial
Seed propagated
Vegetatively propagated
Vine / climber
Woody

Distribution

Top of page No attempt has been made to differentiate between the two Hedera taxa in the distribution records. McAllister (1990) noted that H. helix subsp. helix is widespread throughout much of Europe and H. hibernica occurs along the Atlantic Coast of Europe with much range overlap. However, being such an important horticultural taxon, H. hibernica is probably now widely planted throughout much of western Europe. H. helix subsp. rhizomatifera is restricted to southern Spain and H. helix f. poetarum is found in Italy and western Transcaucasia. The general distribution of these closely related taxa is given by Ackerfield and Wen (2002). The species is likely to be more widespread than indicated in the distribution table.

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasivePlantedReferenceNotes

Asia

ArmeniaPresentNative Natural USDA-ARS, 2003
Georgia (Republic of)PresentNative Natural USDA-ARS, 2003
IsraelPresentNative Natural USDA-ARS, 2003
JapanPresentIntroducedTakeuchi and Horie, 1998
LebanonPresentNative Natural USDA-ARS, 2003
SyriaPresentNative Natural USDA-ARS, 2003
TurkeyWidespreadNative Natural Tutin et al., 1968
VietnamPresentNativeMissouri Botanical Garden, 2003

Africa

AlgeriaPresentNative Natural USDA-ARS, 2003
LibyaPresentNative Natural USDA-ARS, 2003
MoroccoPresentNative Natural USDA-ARS, 2003
Spain
-Canary IslandsPresentNativeUSDA-ARS, 2003
TunisiaPresentNative Natural USDA-ARS, 2003

North America

CanadaPresentPresent based on regional distribution.
-British ColumbiaRestricted distributionIntroduced Invasive Murray and Jones, 2002
-OntarioRestricted distributionIntroduced Invasive Anon., 2002
USAPresentPresent based on regional distribution.
-AlabamaPresentIntroducedUSDA-NRCS, 2002
-AlaskaPresentIntroducedUSDA-NRCS, 2002
-ArizonaPresentIntroducedUSDA-NRCS, 2002
-CaliforniaPresentIntroduced Invasive Reichard, 2000; USDA-NRCS, 2002
-FloridaPresentIntroducedUSDA-NRCS, 2002
-GeorgiaPresentIntroducedUSDA-NRCS, 2002
-HawaiiPresentIntroduced Invasive USDA-NRCS, 2002; Starr et al., 2003
-IllinoisPresentIntroducedUSDA-NRCS, 2002
-IndianaPresentIntroducedUSDA-NRCS, 2002
-KentuckyPresentIntroducedUSDA-NRCS, 2002
-LouisianaPresentIntroducedUSDA-NRCS, 2002
-MarylandPresentIntroducedUSDA-NRCS, 2002
-MassachusettsPresentIntroducedUSDA-NRCS, 2002
-MichiganPresentIntroducedUSDA-NRCS, 2002
-MississippiPresentIntroducedUSDA-NRCS, 2002
-MissouriPresentIntroducedUSDA-NRCS, 2002
-New JerseyPresentIntroducedUSDA-NRCS, 2002
-New YorkPresentIntroducedUSDA-NRCS, 2002
-North CarolinaPresentIntroducedUSDA-NRCS, 2002
-OhioPresentIntroducedUSDA-NRCS, 2002
-OregonPresentIntroduced Invasive Moriarty, 2001; USDA-NRCS, 2002
-PennsylvaniaPresentIntroducedUSDA-NRCS, 2002
-South CarolinaPresentIntroducedUSDA-NRCS, 2002
-TennesseePresentIntroducedUSDA-NRCS, 2002
-TexasPresentIntroducedUSDA-NRCS, 2002
-UtahPresentIntroducedUSDA-NRCS, 2002
-VirginiaPresentIntroducedUSDA-NRCS, 2002
-WashingtonPresentIntroducedUSDA-NRCS, 2002
-West VirginiaPresentIntroducedUSDA-NRCS, 2002

South America

ArgentinaRestricted distributionIntroduced Invasive Zalba and Villamil, 2002
BoliviaPresentNativeMissouri Botanical Garden, 2003
ChilePresentIntroduced Invasive Pauchard and Alaback, 2002
EcuadorPresentNativeMissouri Botanical Garden, 2003

Europe

AlbaniaWidespreadNative Natural Tutin et al., 1968
AndorraWidespreadNativeTutin et al., 1968
AustriaWidespreadNative Natural Tutin et al., 1968
BelarusWidespreadNative Natural Tutin et al., 1968
BelgiumWidespreadNative Natural Tutin et al., 1968
Bosnia-HercegovinaWidespreadNativeTutin et al., 1968
BulgariaWidespreadNative Natural Tutin et al., 1968
CroatiaWidespreadNativeTutin et al., 1968
CyprusPresentNative Natural USDA-ARS, 2003
Czech RepublicWidespreadNativeTutin et al., 1968
Czechoslovakia (former)Present Natural
DenmarkWidespreadNative Invasive Tutin et al., 1968; Hartvig, 2002
EstoniaWidespreadNativeTutin et al., 1968
FranceWidespreadNative Natural Tutin et al., 1968
-CorsicaWidespreadNativeTutin et al., 1968
GermanyWidespreadNative Natural Tutin et al., 1968
GreeceWidespreadNative Natural Tutin et al., 1968
HungaryWidespreadNative Natural Tutin et al., 1968
IrelandWidespreadNative Natural Stace, 1997
ItalyWidespreadNative Natural Tutin et al., 1968
LatviaWidespreadNative Natural Tutin et al., 1968
LiechtensteinWidespreadNativeTutin et al., 1968
LithuaniaWidespreadNative Natural Tutin et al., 1968
LuxembourgWidespreadNativeTutin et al., 1968
MacedoniaWidespreadNativeTutin et al., 1968
MoldovaWidespreadNative Natural Tutin et al., 1968
NetherlandsWidespreadNative Natural Tutin et al., 1968
NorwayWidespreadNative Natural Tutin et al., 1968
PolandWidespreadNative Natural Tutin et al., 1968
PortugalWidespreadNative Natural Tutin et al., 1968
-AzoresPresentNativeUSDA-ARS, 2003
-MadeiraPresentNativeUSDA-ARS, 2003
RomaniaWidespreadNative Natural Tutin et al., 1968
Russian FederationPresent Natural
-Central RussiaWidespreadNativeTutin et al., 1968
-Southern RussiaPresentNativeUSDA-ARS, 2003
SlovakiaWidespreadNativeTutin et al., 1968
SloveniaWidespreadNativeTutin et al., 1968
SpainWidespreadNative Natural Tutin et al., 1968
SwedenWidespreadNative Natural Tutin et al., 1968
SwitzerlandWidespreadNative Natural Tutin et al., 1968
UKWidespreadNative Natural Stace, 1997
-Channel IslandsWidespreadNativeTutin et al., 1968
UkraineWidespreadNative Natural Tutin et al., 1968
Yugoslavia (former)Present Natural
Yugoslavia (Serbia and Montenegro)WidespreadNativeTutin et al., 1968

Oceania

AustraliaPresentIntroduced Invasive Adler and Stephens, 2001
-New South WalesPresentIntroduced Invasive Turton et al., 2001
-VictoriaPresentIntroduced Invasive Freshwater, 1991
New ZealandRestricted distributionIntroduced Invasive Williams et al., 2002

History of Introduction and Spread

Top of page H. helix is native to Europe, North Africa and the Near East (USDA-ARS, 2003). It was brought to North America by colonial settlers (Morisawa, 1999), but the exact date of introduction and subsequent timing and pattern of distribution within North America is unknown. During the 1900s, it was widely planted throughout the USA (Reichard, 2000; Moriarty, 2001) and it is commonly found near old and existing habitations where it often escapes; infestations are more prevalent in forest parks close to urban centres (Akerson and Gounaris, 2000). In New Zealand, H. helix was introduced as an ornamental species, being first recorded in the wild in 1873, but in the Auckland Region it is thought to have become invasive more recently, i.e. between 1940 and 1970. The species is now found throughout the North Island and parts of the South Island (Anon., n.d.). Hedera taxa including many horticultural varieties have been introduced throughout much of Europe and are known to spread (Clement and Foster, 1994). In Denmark, seeds from garden cultivars spread into natural plant communities and non-native populations have become established (Hartvig, 2002).

Risk of Introduction

Top of page In the USA, over 100 commercially popular Hedera cultivars (mainly H. helix) are available and The American Ivy Society is dedicated to this group of plants including the registration of new Hedera cultivars (Pennisi et al., 2001). This clearly indicates the potential for new introductions of plants from this genus. In Oregon, the Department of Agriculture has declared H. helix a noxious weed; however, State agencies have carried on with the use of this plant in landscaping. Moriarty (2001) reported that an effort was being made to have the plant placed on the noxious weed quarantine list, "making it illegal to bring ivy into the state, offer it for sale, sell it, purchase it, or propagate it." However, because H. helix is a popular landscape plant it was expected that some Oregon nurseries and plant retailers would lobby strongly against such a classification. In Washington, H. helix is on the State Noxious Weed List and native plant alternatives are being promoted (Anon., 2002) and control is not required but is strongly recommended (Anon., 2002; Simon, 2002). In the Auckland Region of New Zealand, H. helix "is no longer permitted to be sold, propagated, distributed or commercially displayed on the basis that it is now a Regional Surveillance Plant Pest" but landowners are encouraged to control infestations of this plant without legal obligation (Auckland Regional Council, 2003).

Habitat

Top of page This versatile plant is commonly found in a variety of natural and human-induced habitats. It is a common forest species, growing on the forest floor or up the trunks of canopy trees. It is readily found on rocks and cliffs including those located in the close vicinity of the sea. In human-dominated habitats it is readily found on walls, houses, fences, posts, hedges and ornamental trees.

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Terrestrial
Terrestrial – ManagedManaged forests, plantations and orchards Present, no further details Harmful (pest or invasive)
Disturbed areas Present, no further details Harmful (pest or invasive)
Rail / roadsides Present, no further details Harmful (pest or invasive)
Urban / peri-urban areas Present, no further details Harmful (pest or invasive)
Terrestrial ‑ Natural / Semi-naturalNatural forests Present, no further details Harmful (pest or invasive)
Riverbanks Present, no further details Harmful (pest or invasive)
Littoral
Coastal areas Present, no further details Harmful (pest or invasive)

Hosts/Species Affected

Top of page When fully grown in a tree, it may adversely affect the canopy of a variety of species by shading out part of the host's foliage. In exposed sites, the vine will increase the likelihood of windthrow of deciduous species, especially of trees in open conditions during winter when there is no foliage and storms are more frequent. There is some evidence to suggest that H. helix has an allelopathic effect on seed germination (Le and Sonu, 2002). Although generally an environmental weed, it may also affect plantation trees.

Biology and Ecology

Top of page Genetics

The respective chromosome numbers of H. helix and H. hibernica are 2n=48 and 2n=96, suggesting that H. helix is the more ancient species, and H. hibernica may have evolved from it via chromosome doubling or hybridization with another Hedera species. The amount of nuclear DNA is 3.6 pg (Grime et al., 1988).

Physiology and Phenology

H. helix exhibits strong heterophily and intermediate shoots and leaves are rare. If a reproductive shoot is detached and roots, it will continue to grow with leaves and shoots typical of that phase. However, 'reversion' to the juvenile vegetative phase can be induced by spraying the plant with the growth hormone gibberellic acid, and abscisic acid reverses the effects. This suggests that the balance of gibberellic acid and abscisic acid is involved in the change from juvenile to mature stage (Briggs and Walters, 1997). In Europe, at its northern, eastern and high altitude distribution limits, the species will remain at its juvenile phase (Andergassen and Bauer, 2002). Flowering and fruiting occur over a number of months with flowering taking place during autumn and early winter. On some plants the distal part of the inflorescence may bear fruits that are already fully-grown when the last flowers on the rest of the inflorescence are just at anthesis. Berry-like fruits ripen in the following spring, April to June in Western Europe (Grime et al., 1988). Germination is epigeal and it takes 6 days for 50% of samples to germinate, and is to some extent inhibited by light (Grime et al., 1988).

Reproductive Biology

A combination of sexual reproduction and vegetative propagation ensures the spread of this species. Age of first reproduction is variable but can be in the region of 10 years (Reichard, 2000). Flowers are insect pollinated and are visited by a variety of insect species, many of which visit the flowers for its nectar (Proctor and Yeo, 1973). A wide number of insects will visit the flowers as they are produced aseasonally when few if any other species are in flower, provided the weather conditions are conducive. In Britain, frequent visitors include the common wasp (Vespula sp.), the hornet (Vespa crabro), the blow-fly (Calliphora sp.), the crane fly (Tipulidae), Tilupa sp. and Dilophus febrilis. However, it is probably mostly pollinated by bees (Apis spp.). Green fruits are born through the winter, ripening in early spring and are readily dispersed by a variety of birds. Up to 70% of the seeds are viable but scarification appears to be essential for germination and this is achieved when seeds pass through a bird's digestive system (Reichard, 2000). Germination mostly takes place in spring (Grime et al., 1988).

Environmental Requirements

H. helix appears to be tolerant of a rather broad spectrum of environmental conditions in the temperate zone. It occurs from sea-level to altitudes of over 1000 m in Europe and has been found up to 3300 m in Bolivia (Missouri Botanical Garden, 2003). It is readily found across a variety of rainfall zones in Europe. It is often found in riparian zones but it does not grow well in areas where the water table is high and soil is waterlogged (Thomas, 1980). It is reported as growing well in acidic and basic soils (Reichard, 2000) and tolerates a wide range of soil pH, but is most frequent and abundant above pH 6 and is seldom found below pH 4 (Grime et al., 1988). In North America (Midwest and New England states) it is reported that severe winter cold inhibits its spread (Moriarty, 2001) and in late autumn, flowers are susceptible to frost (Grime et al., 1988). It is tolerant of salt deposition. The increased winter light under deciduous trees apparently allows this evergreen vine to grow rapidly upward in winter (Thomas, 1980). Although H. helix grows much better in higher light intensities, it is markedly tolerant of shade as well as drought (Thomas, 1980; Sack and Grubb, 2002). It is often considered as a nitrogen indicator species, and plant density has increased over time in forests where nitrogen deposition has increased since the late 1970s (Lameire et al., 2000).

Associations

The rootlets bear vascular-arbuscular mycorrhiza (Grime et al., 1988). In England, H. helix becomes established once a woodland canopy has been produced following tree establishment in open vegetation (Harmer et al., 2001) and often spreads from the woodland's edge (Grime et al., 1988).

Latitude/Altitude Ranges

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Latitude North (°N)Latitude South (°S)Altitude Lower (m)Altitude Upper (m)
0 3300

Air Temperature

Top of page
Parameter Lower limit Upper limit
Absolute minimum temperature (ºC) -35

Rainfall Regime

Top of page Uniform
Winter

Soil Tolerances

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Soil drainage

  • free
  • impeded

Soil reaction

  • acid
  • alkaline
  • neutral

Soil texture

  • heavy
  • light
  • medium

Special soil tolerances

  • shallow

Notes on Natural Enemies

Top of page H. helix suffers from a variety of pests and diseases (Pennisi et al., 2001), but these appear to have little impact on the health of the species apart from affecting the ornamental value of the plant.

Means of Movement and Dispersal

Top of page Natural Dispersal (Non-Biotic)

Stem fragments may possibly be dispersed by running water but there are no documented cases of local dispersal by these means.

Vector Transmission (Biotic)

H. helix is bird-dispersed although its berries are mildly toxic. This mild toxicity can prevent consumption of too many fruits in one period of foraging and regulate seed retention time, thus ensuring better seed dispersal (Barnea et al., 1993). In North America, the fruits do not provide a valuable food source for native songbirds; however, starlings, cedar waxwings, robins and Stellar's jays consume them (Moriarty, 2001) and presumably disperse them.

Accidental Introduction

Vegetative material which can easily root can be readily dispersed accidentally to new suitable habitats. Careless dumping of surplus trimmings from gardens is a major risk (Auckland Regional Council, 2003) but soil movement or transport of logs bearing H. helix stems may also result in the establishment of new infestations. In the USA, recommendations have been given to the public for the safe disposal of garden clippings (Simon, 2002).

Intentional Introduction

The species is widely used as an ornamental and therefore likely to be introduced more widely unless legislation is set up to prevent further introductions.

Pathway Vectors

Top of page
VectorNotesLong DistanceLocalReferences
Soil, sand and gravel Yes

Impact Summary

Top of page
CategoryImpact
Animal/plant collections None
Animal/plant products None
Biodiversity (generally) Negative
Crop production None
Environment (generally) Negative
Fisheries / aquaculture None
Forestry production None
Human health None
Livestock production None
Native fauna Negative
Native flora None
Rare/protected species None
Tourism None
Trade/international relations None
Transport/travel None

Impact

Top of page Although generally an environmental weed, it may also affect plantation trees, though costs of H. helix control in commercial forestry plantations have not been documented.

Environmental Impact

Top of page This species is often viewed as having a high potential impact on the environment and more specifically in completely covering the forest floor and climbing to the tops of the tallest trees, smothering them. Smothering and causing tree dieback or even tree death is an impact not readily reported from its native range. It is widely thought that the dense carpet often produced in some forests suppresses natural regeneration of understorey and forest species maybe as a result of increased nitrogen levels produced by its leaf litter (Thomas, 1980; Akerson and Gounaris, 2000; Reichard, 2000). H. helix has a competitive impact on native plants but this is variable, with various species exhibiting contrasting growth responses (Le and Sonu, 2002). In North America it is thought that the additional weight of water and/or ice on the evergreen leaves may increase storm damage to trees (Reichard, 2000) and a number of other impacts have been postulated by Simon (2002).

Impact: Biodiversity

Top of page H. helix is one of a number of invasive species that are threatening populations of the shrub Epacris hamiltonii in the Australian Blue Mountains, west of Sydney. Only just over 4000 individuals of this endangered shrub are known to grow on cliff edges along three adjacent valleys (Turton et al., 2001). In North America this vine is widely viewed as reducing native plant diversity which in turn reduces habitats for native wildlife species (Moriarty, 2001) and is often said to produce "ivy deserts" (Okerman, 2000; Reichard, 2000).

Threatened Species

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Threatened SpeciesConservation StatusWhere ThreatenedMechanismReferencesNotes
Hexastylis naniflora (dwarf-flowered heartleaf)NatureServe NatureServe; USA ESA listing as threatened species USA ESA listing as threatened speciesNorth Carolina; South CarolinaCompetition - monopolizing resourcesUS Fish and Wildlife Service, 2011

Social Impact

Top of page All parts of the plant are toxic to man (Schepens, 1997). Generally when the fruits are eaten, this results in a combination of stomach pain, nausea, vomiting and diarrhoea. Ingested leaves induce a narcotic effect not unlike that of atropine (Jordan, 1976) and H. helix can cause contact dermatitis, with repeated exposure to wet leaves causing vesicular eruption of the face, hands and arms within 48 hours of contact (Benezra et al., 1985). People most likely to be affected are children who clamber up walls or trees covered with ivy or adults who cut back the plant. Schepens (1997) provides a detailed overview of the toxic properties of H. helix including the symptoms caused and necessary cures. In Australia, where it is introduced and a common plant used by the nursery and garden industry, it is listed as a plant of concern to human health (Adler and Stephens, 2001).

Risk and Impact Factors

Top of page Invasiveness
  • Invasive in its native range
  • Proved invasive outside its native range
  • Highly adaptable to different environments
  • Highly mobile locally
  • Has high reproductive potential
Impact outcomes
  • Negatively impacts human health
  • Negatively impacts animal health
  • Reduced native biodiversity
  • Threat to/ loss of endangered species
  • Threat to/ loss of native species
Impact mechanisms
  • Competition - monopolizing resources
Likelihood of entry/control
  • Highly likely to be transported internationally deliberately
  • Difficult/costly to control

Uses

Top of page H. helix is of major importance in horticulture in much of the temperate zone both for private planting and community landscaping (Moriarty, 2001), as a popular ornamental and groundcover in residential, commercial and public landscaping, and has been used to control erosion in many parts of the USA (Reichard, 2000; Moriarty, 2001). It does provide a complete ground cover; however, its shallow rooting does not prevent landslides when the soils are saturated following periods of heavy rainfall (Moriarty, 2001). Historically, extracts from the foliage were used medicinally to treat wounds and ulcerative sores, combat lice and fleas, as a narcotic to soothe toothaches, against arthritis and rheumatism and recently it has been shown to be effective against bronchitis (Büechi and Bolli, 2003). Bees readily visit flowers and the resulting honey is a fine pale amber colour with an excellent flavour and there seems to be no record of toxins being transferred to the honey (Jordan, 1976; Schepens, 1997). Currently, plant extracts have only limited use as ingredients in some cosmetics, shampoos and medicines (Schepens, 1997).

Uses List

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Materials

  • Poisonous to mammals

Medicinal, pharmaceutical

  • Traditional/folklore

Similarities to Other Species/Conditions

Top of page Species of the genus Hedera are difficult to tell apart and require close examination to identify to species level. Ackerfield and Wen (2002) have recently produced a key to facilitate identification and Pennisi et al. (2001) provide brief descriptions of scores of ornamental varieties.

Prevention and Control

Top of page Cultural Control

Although the palatability of H. helix to grazing animals in North America is unrecorded (Reichard, 2000), European deer species find it edible and its biomass decreases markedly when ungulate numbers are high (González-Hernández and Silva-Pando, 1996). Mammal herbivory could well decrease the plant's vigour in its invasive range.

Mechanical Control

Killing the aerial portion of H. helix, the seed-producing part of the plant, is easy and only requires the cutting of the stems around the host tree with pruning tools. However, when H. helix grows on tree-ferns, it is not sufficient to cut the stems to kill the plant. All parts of the plant must be removed as H. helix can root and sustain itself in the fibrous tree-fern trunks. The roots of young plants can be easily dug out, particularly when the soil is moist, from the ground around the base of the infected tree, whereas old individuals generally do not resprout. When the plant carpets the forest floor, individual stems can be readily pulled off the ground; however, it is essential to remove all runners. Any overlooked live shoot may restart an infestation, thus follow-up monitoring and control is essential. Small or young ivy plants can be pulled off supporting structures or trees, and roots dug out. Soil and native vegetation disturbance must be as limited as possible because this favours the establishment of other invasive species. To avoid rerooting and resprouting, all material must be carefully removed from the site and disposed of safely. If removal of the plants is not possible, all parts of the plant must be placed off the ground in such a way that they can dry out. Gloves should be worn as skin irritation may follow contact with the plant (Freshwater, 1991; Morisawa, 1999; Reichard, 2000). One form of prescribed burning has successfully been used to control H. helix. Plants and resprouts are repeatedly burnt with a blowtorch until the plant's resources are exhausted (Reichard, 2000).

Chemical Control

The mechanical control of H. helix by cutting stems is not always successful especially if the roots of younger individuals cannot be removed. Then it is advisable to strip the bark, notch the exposed section of the vine and paint on an undiluted herbicide such as glyphosate. This combination of cutting the vine less than 20 cm above ground and an immediate herbicide application may provide better control. Metsulfuron, picloram and glyphosate have all proved successful in Australia (Anon., n.d.). As H. helix leaves are waxy, this often prevents the herbicides, especially hydrophilic compounds such as glyphosate, from permeating the leaves. Thus this plant does not respond well to herbicide spraying, even when a surfactant is added, and non-target native species may be affected in the process. When desirable native vegetation must not be harmed then the stump treatments should be used wherever possible. It is apparent that older plants are more resistant to herbicide treatment and even two applications may not kill them but just reduce growth. In the western USA, immediate spraying of triclopyr following the removal of most leaves and young shoots with a string trimmer has proved successful. However, in other instance, applications of glyphosate, triclopyr and 2,4-D have proved ineffective or unsatisfactory (Morisawa, 1999; Reichard, 2000).

Biological Control

There has been no attempt to identify and introduce biological control agents, and in view of the species' importance in horticulture in the USA, it is extremely unlikely that any such attempts will be made in that country (Reichard, 2000). In view of the species' near immunity to pests and diseases in its native range, prospects for biological control are limited. Prasad (2002) has reported that the use of a bioherbicide in the form of the fungus Chondrostereum purpureum has been applied to H. helix but its efficacy has yet to be ascertained.

References

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