Hedera helix L. Family - Araliaceae. Common Names - English ivy, ivy.

Answer

Score

1.01

Is the species highly domesticated? (If answer is 'no' then go to question 2.01)

y

-3

1.02

Has the species become naturalized where grown?

y

1

1.03

Does the species have weedy races?

y

1

2.01

Species suited to tropical or subtropical climate(s) (0-low; 1-intermediate; 2-high) – If island is primarily wet habitat, then substitute “wet tropical” for “tropical or subtropical”

1

2.02

Quality of climate match data (0-low; 1-intermediate; 2-high) see appendix 2

2

2.03

Broad climate suitability (environmental versatility)

y

1

2.04

Native or naturalized in regions with tropical or subtropical climates

y

1

2.05

Does the species have a history of repeated introductions outside its natural range? y=-2

y

3.01

Naturalized beyond native range y = 1*multiplier (see Append 2), n= question 2.05

y

1

3.02

Garden/amenity/disturbance weed y = 1*multiplier (see Append 2)

3.03

Agricultural/forestry/horticultural weed y = 2*multiplier (see Append 2)

y

2

3.04

Environmental weed y = 2*multiplier (see Append 2)

y

2

3.05

Congeneric weed y = 1*multiplier (see Append 2)

y

1

4.01

Produces spines, thorns or burrs

n

0

4.02

Allelopathic

y

1

4.03

Parasitic

n

0

4.04

Unpalatable to grazing animals

n

-1

4.05

Toxic to animals

y

1

4.06

Host for recognized pests and pathogens

y

1

4.07

Causes allergies or is otherwise toxic to humans

y

1

4.08

Creates a fire hazard in natural ecosystems

n

0

4.09

Is a shade tolerant plant at some stage of its life cycle

y

1

4.1

Tolerates a wide range of soil conditions (or limestone conditions if not a volcanic island)

y

1

4.11

Climbing or smothering growth habit

y

1

4.12

Forms dense thickets

n

0

5.01

Aquatic

n

0

5.02

Grass

n

0

5.03

Nitrogen fixing woody plant

n

0

5.04

Geophyte (herbaceous with underground storage organs -- bulbs, corms, or tubers)

n

0

6.01

Evidence of substantial reproductive failure in native habitat

n

0

6.02

Produces viable seed.

y

1

6.03

Hybridizes naturally

6.04

Self-compatible or apomictic

n

-1

6.05

Requires specialist pollinators

n

0

6.06

Reproduction by vegetative fragmentation

y

1

6.07

Minimum generative time (years) 1 year = 1, 2 or 3 years = 0, 4+ years = -1

4

-1

7.01

Propagules likely to be dispersed unintentionally (plants growing in heavily trafficked areas)

7.02

Propagules dispersed intentionally by people

y

1

7.03

Propagules likely to disperse as a produce contaminant

n

-1

7.04

Propagules adapted to wind dispersal

n

-1

7.05

Propagules water dispersed

7.06

Propagules bird dispersed

y

1

7.07

Propagules dispersed by other animals (externally)

n

-1

7.08

Propagules survive passage through the gut

y

1

8.01

Prolific seed production (>1000/m2)

8.02

Evidence that a persistent propagule bank is formed (>1 yr)

n

-1

8.03

Well controlled by herbicides

y

-1

8.04

Tolerates, or benefits from, mutilation, cultivation, or fire

n

-1

8.05

Effective natural enemies present locally (e.g. introduced biocontrol agents)

Total score:

10

Notes

Reference

1.01

(1)Native from Europe to the Caucasus Mountains, widely cultivated as an ornamental since ancient times; in Hawaii cultivated at least since the early 1900s and now very sparingly naturalized on Kauai, Oahu, and Hawaii. (2)Hundreds of cultivars of H. helix and its subspecies are recognized in the horticultural trade. (3)Many of the species in the genus Hedera are widely distributed and adaptable. The species H. helix is noted to have over 400 variants or cultivars each numbered and accounted for by the American Ivy Society (AIS) and each with slightly different ecological tolerances (Laroque, 1998; American Ivy Society, 1999). The adaptability of this species or “ecological plasticity” results in its popularity as an ornamental among landscapers and horticulturists as it is adept at filling so many rolls and versatile enough to find a niche in almost any space [or] climate (Wellingham-Jones, 1985).

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. (2)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648. (3)http://horticulture.cfans.umn.edu/vd/h5015/00papers/okerman.htm [3 Jan 2008]

1.02

(1)Native from Europe to the Caucasus Mountains, widely cultivated as an ornamental since ancient times; in Hawaii cultivated at least since the early 1900s and now very sparingly naturalized on Kauai, Oahu, and Hawaii. (2)Previously reported as sparingly naturalized on Kaua‘i, O‘ahu, and Hawai‘i (Wagner et al., 1999), H. helix (English ivy) commonly escapes cultivation in Olinda, Maui where it can be found in Eucalyptus forest along Pi‘iholo Rd Fruits have recently been collected on both cultivated and naturalized plants. According to Pat Bily (pers.comm.), the seeds are viable. (3)Ivy has naturalized and become common in Australia, Brazil, Canada, Hawaii, New Zealand and the United States (Laroque 1998, cited in Grivet & Petit 2002), and has also been introduced to India and South Africa.

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. (2)Starr, F., K. Starr, and L. L. Loope. 2003. New plant records from the Hawaiian Archipelago. In: Evenhuis, Neal L. and Eldredge, Lucius G., eds. Records of the Hawaii Biological Survey for 2001-2002. Part 2: Notes. Bishop Museum Occasional Papers. 74:23-34. (3)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

1.03

(1)we would like to caution against considering H. helix as less invasive. We observed that the characteristics which make particular cultivars grow slower, such as self-branching, tend not to be found in wild populations. There is also a possibility for particular cultivars to cross with more aggressive cultivars as they reach a reproductive state, especially because ivy is actively spreading via fruits (T. Fletcher, personal communication).

(1)Clarke, M. M., S. H. Reichard, and C. W. Hamilton. 2006. Prevalence of different horticultural taxa of ivy (Hedera spp., Araliaceae) in invading populations. Biological Invasions 8 (2) : 149-157.

2.01

(1)Native from Europe to the Caucasus Mountains, widely cultivated as an ornamental since ancient times; in Hawaii cultivated at least since the early 1900s and now very sparingly naturalized on Kauai, Oahu, and Hawaii.

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu.

2.02

Native range is well known.

2.03

(1)Hardiness: USDA Zone 5a: to -28.8 °C (-20 °F) USDA Zone 5b: to -26.1 °C (-15 °F) USDA Zone 6a: to -23.3 °C (-10 °F) USDA Zone 6b: to -20.5 °C (-5 °F) USDA Zone 7a: to -17.7 °C (0 °F) USDA Zone 7b: to -14.9 °C (5 °F) USDA Zone 8a: to -12.2 °C (10 °F) USDA Zone 8b: to -9.4 °C (15 °F) USDA Zone 9a: to -6.6 °C (20 °F) USDA Zone 9b: to -3.8 °C (25 °F) (2)Ivy is intolerant of winter cold (mean temperature of coldest month ≤ −2 °C, Iversen 1944), this factor appearing to determine the limits to its northern and eastern distribution in Europe (see also Hafsten 1956). Ellenberg (1988) suggested that winter frosts may cause the trend for ivy to cease climbing trees and become more of a terrestrial creeper as it moves east in Europe. Flowers produced late in the autumn are susceptible to frost (Grime et al. 1988) and early ripening fruit may be caused to wither and abort by excessive cold (Snow & Snow 1988). However, induced tolerance may permit survival of temperatures down to −25 °C, as a result of increasing concentrations of watersoluble proteins and sugars in the leaves (Parker 1962; Street & Öpik 1984)...As befits a member of a largely tropical family, ivy benefits from warm summers and is disadvantaged by frosty winters. Although weeks of mild frosts appear to limit the distribution of ivy, tolerance of much more severe frosts may be induced.

(1)http://davesgarden.com/guides/pf/go/1637/ [2 Jan 2008] (2)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

2.04

(1)Native from Europe to the Caucasus Mountains, widely cultivated as an ornamental since ancient times; in Hawaii cultivated at least since the early 1900s and now very sparingly naturalized on Kauai, Oahu, and Hawaii. (2)Previously reported as sparingly naturalized on Kaua‘i, O‘ahu, and Hawai‘i (Wagner et al., 1999), H. helix (English ivy) commonly escapes cultivation in Olinda, Maui where it can be found in Eucalyptus forest along Pi‘iholo Rd Fruits have recently been collected on both cultivated and naturalized plants. According to Pat Bily (pers.comm.), the seeds are viable.

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. (2)Starr, F., K. Starr, and L. L. Loope. 2003. New plant records from the Hawaiian Archipelago. In: Evenhuis, Neal L. and Eldredge, Lucius G., eds. Records of the Hawaii Biological Survey for 2001-2002. Part 2: Notes. Bishop Museum Occasional Papers. 74:23-34.

2.05

(1)Another prominent invader is the ‘English’ ivy complex (Hedera spp.), evergreen woody vines native to Eurasia, which were introduced into North America as an ornamental plant in early colonial times (Reichard 2000). Several similar forms are sold under the general common name of English ivy. They are groundcovers that have been used extensively in urban landscapes in the Pacific Northwest because of many desirable characteristics, including appearance, shade-tolerance, and easy propagation and growth. They have also been used for erosion control and slope stabilization, although their effectiveness in that role appears overrated (Parker 1996). (2)Ivy has naturalized and become common in Australia, Brazil, Canada, Hawaii, New Zealand and the United States (Laroque 1998, cited in Grivet & Petit 2002), and has also been introduced to India and South Africa.

(1)Clarke, M. M., S. H. Reichard, and C. W. Hamilton. 2006. Prevalence of different horticultural taxa of ivy (Hedera spp., Araliaceae) in invading populations. Biological Invasions 8 (2) : 149-157. (2)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

3.01

(1)Native from Europe to the Caucasus Mountains, widely cultivated as an ornamental since ancient times; in Hawaii cultivated at least since the early 1900s and now very sparingly naturalized on Kauai, Oahu, and Hawaii. (2)Previously reported as sparingly naturalized on Kaua‘i, O‘ahu, and Hawai‘i (Wagner et al., 1999), H. helix (English ivy) commonly escapes cultivation in Olinda, Maui where it can be found in Eucalyptus forest along Pi‘iholo Rd Fruits have recently been collected on both cultivated and naturalized plants. According to Pat Bily (pers.comm.), the seeds are viable. (3)Ivy has naturalized and become common in Australia, Brazil, Canada, Hawaii, New Zealand and the United States (Laroque 1998, cited in Grivet & Petit 2002), and has also been introduced to India and South Africa.

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the flowering plants of Hawaii. Revised edition. Bernice P. Bishop Museum special publication. University of Hawai‘i Press/Bishop Museum Press, Honolulu. (2)Starr, F., K. Starr, and L. L. Loope. 2003. New plant records from the Hawaiian Archipelago. In: Evenhuis, Neal L. and Eldredge, Lucius G., eds. Records of the Hawaii Biological Survey for 2001-2002. Part 2: Notes. Bishop Museum Occasional Papers. 74:23-34. (3)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

3.02

Invades disturbed habitats as an Environmental Weed (see question 3.04). (1)Currently, it is found in 24 states and is listed as a noxious weed in Oregon and California, even reaching quarantined status in Oregon (USDA, NCRS 2006). Because ivy is more likely to invade disturbed forests, its spread through the southeastern United States has been helped dramatically by the region's history of extensive logging and human habitation (Thomas, 1998). (2)English ivy outcompetes both grasses, herbs and trees, often reducing animal feeding habitats. In warm areas, H. helix can grow throughout the year and probably outcompetes native vegetation that is dormant during the winter. In Australia, English ivy is found in disturbed areas of the forest. Seeds are often spread into these areas by birds or other animals. H. helix is a pest in Europe but only in disturbed habitats.

(1)Biggerstaff, M. S. and C. W. Beck. 2007. Effects of English ivy (Hedera helix) on seed bank formation and germination. American Midland Naturalist 157 (2) : 250-257 (2)http://tncweeds.ucdavis.edu/moredocs/hedhel01.pdf [3 Jan 2007]

3.03

(1)English ivy is an aggressive invader that threatens nearly all forested habitat types in the northwestern U.S. up to at least 3000' in elevation (900 meters). English ivy cover is rapidly reaching catastrophic levels, especially in urban and near urban areas of the Pacific Northwest. Without prompt action, many thousands of trees will be toppled or killed over the next decade in the Portland metro area alone...In the end, the results of societal passivity regarding ivy will be extensive loss of shade trees, declines in native flora and fauna, water quality and forest productivity; and increases in erosion, slope failures and landscaping / management costs for private citizens, the forest industry and public agencies alike.

(1)http://tncweeds.ucdavis.edu/moredocs/hedhel02.pdf [3 Jan 2008]

3.04

(1)In forests in the southeastern United States, English ivy Hedera helix L. is an exotic species that is naturalizing rapidly. Once established, ivy forms a dense ground cover that prevents the emergence of almost all herbs and dramatically reduces light levels (Thomas, 1980). This reduction in light levels can weaken trees and cause collapse either by outright death or by increased susceptibility to damage by ice storms and winds (Penfound, 1966; Sicama et al, 1976; Thomas. 1980; Harmer et ai, 2001). (2)ABSTRACT.—English ivy Hedera helix L. is rapidly invading forest ecosystems in the southeastern United States, leading to a decrease in the diversity of native plant species. To determine the underlying mechanism for the loss of diversity and understand the potential for restoration of impacted habitats, we examined whether ivy had a negative effect on seed hank formation and germination. We sampled the seed bank and the summer and fall seed rains in areas with and without ivy. In addition, we determined potential allelopathic effects of ivy on germination of Coreopsis lancelota seeds. The density and species diversity of
the seed bank and seed rains were not significantly different between areas with and without ivy. However, ivy led to a marginally significant reduction in the germination rate of C. lancelota seeds. Yet, the effect of ivy on germination only occurred when ivy plants were present. Germination rates did not differ in soil from areas with and without ivy. Our results suggest that native plant communities can regenerate naturally from the seed bank if English ivy were removed. (3)English ivy: Class C noxious weed, Washington State, only cultivars 'Baltica', 'Pittsburgh', 'Star'

(1)Biggerstaff, M. S. and C. W. Beck. 2007. Effects of method of English ivy removal and seed addition on regeneration of vegetation in a southeastern piedmont forest. American Midland Naturalist 158 (1) : 206-220. (2)Biggerstaff, M. S. and C. W. Beck. 2007. Effects of English ivy (Hedera helix) on seed bank formation and germination. American Midland Naturalist 157 (2) : 250-257 (3)http://plants.usda.gov/java/profile?symbol=HEHE [3 Jan 2008]

3.05

(1)Abstract: ‘English’ ivy (Hedera spp.) is a complex of invasive plant pests that are separated into several distinct taxa. To better understand the invasion by ivy of Pacific Northwest native forests, we investigated the taxonomic identity of 58 selected invasive populations in the Pacific Northwest. Random amplified polymorphic DNA (RAPD) markers revealed that 83% of the 119 samples from invading populations were derived form H. hibernica (Kirchner) Bean, which has been frequently sold as English ivy, although this apparently is an incorrect common name. It is used widely in urban landscapes in the Northwest. The remaining 20 samples were either H. helix ‘California,’ ‘Pittsburgh,’ ‘Star,’ other cultivars not investigated in the study or possible hybrids.

(1)Clarke, M. M., S. H. Reichard, and C. W. Hamilton. 2006. Prevalence of different horticultural taxa of ivy (Hedera spp., Araliaceae) in invading populations. Biological Invasions 8 (2) : 149-157.

4.01

(1)Woody stems up to 25 cm diameter, young twigs pubescent with stellate to peltate hairs, and densely furnished with adventitious roots. Leaves petiolate, simple, alternate, exstipulate, coriaceous, glabrous, evergreen; those of climbing or creeping stems 4–10 (−25) cm, palmately lobed with 3–5 triangular, entire lobes; leaves of flowering stems 6–10 cm, entire, ovate or rhombic. Leaves shining, dark green above, often with pale veins, paler green below; may become pale green/ yellow in late summer, and upper surface sometimes tinged with purple in winter.

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

4.02

(1)The germination of Coreopsisvias reduced to a marginally significant degree when exposed to English ivy. While physical competition is still a possibility, our experimental design removed competition for light, water and nutrients. Thus, the reduction in germination of Coreopsis suggests a possible allelopathic effect of ivy. Our results coincide with those of Hines (1995), who found decreased germination of radish {Raphanus sp.) and pansy {Viola sp.) in soil mixed with ivy leaves. The possible allelopathic effects of ivy on germination of native plants suggests a mechanism in addition to decreasing light levels (Thomas, 1980; Harmer et al, 2001) by which ivy may exclude native herbaceous species. Even though ivy did have a marginally significant effect on germination rates when present, the allelopathic effects of ivy do not appear to remain in the soil after ivy is removed, as we found no significant difference between the germination rates of seeds sown in soil where ivy had and had not been present. In contrast, Wardle et al (1991) used a similar experimental approach and found significant residual allelopathic effects of six species of pasture grass on seedling emergence of nodding thistle {Carduus nutans). In many cases, the residtial allelopathic effect increased in strength with time since removal of the grasses, perhaps due to the decomposition of exudates from the roots of the grasses (Wardle et al, 1991). Therefore, we might have found a residtial allelopathic effect of ivy if we had stored the soil from ivy plots for a period of time before sowing the Coreopsis seed. However, in a field study, we found that native seedlings rettirned rapidly after removal of ivy (Biggerstaff and Beck, in press), which suggests that any allelopathic chemicals produced by ivy degrade rapidly, rather than increase in strength over time.

(1)Biggerstaff, M. S. and C. W. Beck. 2007. Effects of English ivy (Hedera helix) on seed bank formation and germination. American Midland Naturalist 157 (2) : 250-257

4.03

(1)No evidence. (2) The vine attaches to surfaces but does not penetrate through mortar or tree bark, thus it is not considered to be a parasite

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648. (2)http://horticulture.cfans.umn.edu/vd/h5015/00papers/okerman.htm [3 Jan 2008]

4.04

(1)Despite the presence of a range of secondary metabolites in the foliage, a number of vertebrate species will browse ivy, including red, roe and fallow deer. Roe deer (Capreolus capreolus L.) show a distinct preference for ivy during the autumn and winter, when it may form a significant part of the diet, with mainly foliage but some fruits taken also (Jackson 1980; Hélène Verheyden- Tixier, pers. comm.). However, roe deer show a distinct avoidance in the summer, or take very little (Jackson 1980; Tixier et al. 1997). Fallow deer (Dama dama L.) will also take ivy foliage in winter (Jackson 1980), and red deer (Cervus elephas L.) will supplement their diet with ivy in hard winters, and take lesser amounts in spring and summer (Coleman-Cooke, in Simmons & Dimbleby 1974; cf. Lloyd 1970; Allen 1974; Allen & Floyd 1988). Red and roe deer are capable of significantly reducing the biomass of ivy by grazing (González- Hernández & Silva-Pando 1996). Sheep relish ivy, sick beasts taking ivy leaves when refusing other forage (G.W. Metcalfe, pers. comm.) and sheep may severely restrict ivy colonization of grassland areas and woodland understorey (Hillegers 1989, cited in Bottema 2001). Pike & Godwin (1953) report evidence of ivy in the teeth of a rhinoceros from Clacton-on-Sea, Essex, from the last interglacial, but this probably represents post mortem deposition rather than herbivory.

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

4.05

(1)Cooper & Johnson (1984) report toxicity to cattle (leaves and berries), deer, sheep, dogs and chickens (latter by seeds),

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

4.06

(1)A large number of fungi has been isolated from ivy, some pathogenic and others associated with the breakdown of dead leaves and stem fragments. The main diseases of horticulturally grown ivies are bacterial leaf spot caused by Xanthomonas hederae and X. campestris pv. hedera, and ivy leaf spot fungus Colletotrichum trichellum (Fr.) Duke (Rose 1980; Osborne & Chase 1985; Lopez Carbonell et al. 1998). There is also a rhabdovirus that causes ivy vein clearing virus (IVCV; Russo et al. 1979). (2)Abstract: Cultivars of H. helix L. had variable susceptibilities of Xanthomonas [X. campestris] leaf spot and two-spotted spider mite [Tetranychus urticae] 'Gold Dust', 'Perfection', 'Sweet Heart', 'Eva' and 'California' were relatively resistant to Xanthomonas, whereas 'Ivalace', 'Green Feather', 'Hahn Variegated' and 'Brokamp' were the most susceptible. 'Sweet Heart', 'Telecurl', and 'Gold Dust' were relatively resistant to mite population development, whereas 'Gold Heart', 'Manda Crested' and 'California' were the most susceptible. (3)English ivy also serves as a reservoir for bacterial leaf scorch (Xylella fastidiosa), a plant pathogen that is harmful to native trees such as elms, oaks, and maples.

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648. (2)Osborne, L. S. and A.R. Chase. 1985. SUSCEPTIBILITY OF CULTIVARS OF ENGLISH IVY HEDERA-HELIX TO TWO-SPOTTED SPIDER MITE AND XANTHOMONAS LEAF SPOT. Hortscience 20 (2): 269-271. (3)http://tncweeds.ucdavis.edu/moredocs/hedhel02.pdf [3 Jan 2008]

4.07

(1)Danger: All parts of plant are poisonous if ingested Handling plant may cause skin irritation or allergic reaction (2)The sap of ivy may cause dermatitis in man (Cooper & Johnson 1984), the allergens being the polyacetylenes falcarinol and didehydrofalcarinol (García et al. 1995); skin reactions have also been attributed to the alkaloid emetine (Mahran et al. 1975). Turton (1925) reported the poisoning of a child by eating ivy leaves.

(1)http://davesgarden.com/guides/pf/go/1637/ [2 Jan 2008]

4.08

(1)...being evergreen and with a relatively high water content, ivy is slow to burn and will not readily spread fire well. Consequently, ground planting with ivy has been proposed to reduce fire risk in seasonally dry areas (e.g. Utah Bureau of Land Management 2001).

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

4.09

(1)Ivy grows most vigorously in shaded, moist sites on heavy, fertile soils, and where it occurs in woodland it is frequently dominant in the field layer.

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

4.1

(1)Soil pH requirements: 6.1 to 6.5 (mildly acidic) 6.6 to 7.5 (neutral) 7.6 to 7.8 (mildly alkaline) (2)Ivy is tolerant of all but the most acid (< pH 4), waterlogged or very dry soils. It is favoured by moist fertile or very fertile soils ranging from fairly dry to slightly damp; so it is common on heavier clay-rich soils and less abundant on poor and well-drained sandy soils (Tansley, Br. Isl.; Grime et al. 1988; Snow & Snow 1988).

(1)http://davesgarden.com/guides/pf/go/1637/ [2 Jan 2008] (2)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

4.11

(1)Climbing, sometimes reaching 30 m, or prostrate and creeping, forming extensive carpets. (2)In forests in the southeastern United States, English ivy Hedera helix L. is an exotic species that is naturalizing rapidly. Once established, ivy forms a dense ground cover that prevents the emergence of almost all herbs and dramatically reduces light levels (Thomas, 1980). This reduction in light levels can weaken trees and cause collapse either by outright death or by increased susceptibility to damage by ice storms and winds (Penfound, 1966; Sicama et al, 1976; Thomas. 1980; Harmer et al, 2001). (3)The leaves on the juvenile plant, however, are more adapted to lower light levels characteristic of the forest floor which allow it to spread and form a dense vegetative cover that can eventually be 6” thick (Devero, 2000).

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648. (2)Biggerstaff, M. S. and C. W. Beck. 2007. Effects of method of English ivy removal and seed addition on regeneration of vegetation in a southeastern piedmont forest. American Midland Naturalist 158 (1) : 206-220. (3)http://horticulture.cfans.umn.edu/vd/h5015/00papers/okerman.htm [3 Jan 2008]

4.12

A vine

5.01

Terrestrial

5.02

Araliaceae

5.03

Araliaceae

5.04

(1)No evidence.

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

6.01

(1)No evidence.

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

6.02

(1)Seeds normally start to germinate within 6–14 days of planting, although dormancy of cleaned seeds (manually cleaned or seeds regurgitated by blackbirds or starlings) may last for up to 30 days; cleaning results in nearly 100% germination (Clergeau 1992; D.J. Metcalfe, unpublished data). Seeds planted within the fruits may remain dormant for up to 57 days, associated with c. 40% seed mortality. Drying of fruits kills all seeds (Clergeau 1992). Germination is epigeal, and may to some extent be inhibited by light. There does not appear to be any extended period of seed dormancy or the formation of a soil seed bank (Warr 1991; Kjellson 1992).

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

6.03

Possibly (1)Wild populations show considerable variation, which may in part be due to hybridization, but also to the tendency of juvenile shoots to mutate freely, giving rise to various foliage and growth habits. These may by propagated by cuttings or layers by horticulturists to provide the many commercially available cultivars, of which at least 89 are commonly available (Bailey & Bailey 1976). Hedera helix ssp. helix is a diploid, and although it frequently grows in close proximity to the tetraploid (ssp. hibernica), no triploids have yet been identified (McAllister & Rutherford 1990). However, chloroplast microsatellite markers show some genetic mixing, and shifts in ploidy or hybridization and introgression are possible (Grivet & Petit 2002; references therein). The intergeneric hybrid × Fatshedera lizei, which arose in Lizé Frères nursery, Nantes, in 1910, occurred between Fatsia japonica ‘Moseri’ × Hedera helix cv, but has not been repeated (Mabberley 1997).

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

6.04

(1)These insect visitors effect cross-pollination, as self-pollination would seem to be ineffective (Wittrock 1886, in Knuth, Poll. II). (2)Potential for self-pollination or apomixis: None

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648. (2)Butz Huryn, V. M. and H. Moller. 1995. AN ASSESSMENT OF THE CONTRIBUTION OF HONEY BEES (APIS MELLIFERA) TO WEED REPRODUCTION IN NEW ZEALAND PROTECTED NATURAL AREAS. New Zealand Journal of Ecology 19(2): 111-122.

6.05

(1)Flowers are hermaphrodite, protandrous or homogamous, and are insect pollinated...These insect visitors effect cross-pollination, as self-pollination would seem to be ineffective (Wittrock 1886, in Knuth, Poll. II). A wide range of insects may be seen to visit ivy flowers; often swarms of flies and Hymenoptera are in attendance at sunlit inflorescences

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

6.06

(1)English ivy spreads locally through vegetative growth and new plants can grow from cut or broken pieces of stems that are able to root in the soil. (2)Ivy reproduces either vegetatively via stolons (root-like stems) or through seeds (photograph 9). Roots form when stem nodes contact moist soil, leading to the formation of a dense mat of vegetation. Ivy roots are vigorous resprouters, meaning that a broken root left in the soil will almost certainly grow a new stem.

(1)http://www.nps.gov/plants/ALIEN/fact/hehe1.htm [2 Jan 2008] (2)http://tncweeds.ucdavis.edu/moredocs/hedhel02.pdf

6.07

(1)Vines may grow for up to ten years before producing flowers. (2) While vegetative reproduction is a key to the success of English ivy, the plant also reproduces prolifically by seed. English ivy flowers in fall, and fruits are produced the following spring in April and May. The juvenile period is long, often ten years or more, but when it becomes reproductive, it produces large numbers of bisexual flowers in fall that are attractive to pollinating bees.

(1)http://www.nps.gov/plants/ALIEN/fact/hehe1.htm [3 Jan 2008] (2)http://ucce.ucdavis.edu/datastore/detailreport.cfm?usernumber=55&surveynumber=182 [3 Jan 2008]

7.01

Unknown, but possible that vegetative fragments could be dispersed unintentionally. (1)English ivy grows easily in many types of soil and in sun or shade, and is fairly drought tolerant once established. It is usually found in the wild where people have dumped garden waste.

(1)http://www.pittsburghparks.org/userdocs/4-Vines.pdf [3 Jan 2008]

7.02

Popular ornamental. (1)Today a multitude of growth forms are available, including nonclimbing and slow-growing, ground-hugging types, as well as countless variations in leaf shape and size, variegation, and color patterning. Many of these are in the trade and could appear in local nurseries.

(1)Staples, G.W. and D.R Herbst. 2005. A Tropical Garden Flora: Plants Cultivated in the Hawaiian Islands and Other Tropical Places. Bishop Museum Press, Honolulu.

7.03

No evidence.

7.04

Fleshy fruit adapted for bird dispersal. (1)Fruit a berry, bluish- or greenish black (rarely yellow or white), globose, 6–8 mm. Pulp purple

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

7.05

It may be possible that fruits and/or vegetative fragments are dispersed along watercourses. (1)The ability of H. helix to spread adventitiously and its dispersal from birds causes concern when the plant is used in close proximity to forest or riparian zones.

(1)http://horticulture.cfans.umn.edu/vd/h5015/00papers/okerman.htm [3 Jan 2008]

7.06

(1)Fruit a berry, bluish- or greenish black (rarely yellow or white), globose, 6–8 mm. Pulp purple...Largely dispersed by birds, several ivy seeds may be deposited in a single dropping; all of these may germinate, so clusters of seedlings are frequently found together, at densities of up to 50 m−2 (Bottema 2001)...Seeds are dispersed from November/December until as late as June, although Snow & Snow (1988) recorded a feeding peak in April and most European records are of berry consumption in April and May. In a hard winter the majority of fruit are taken in January and February. The prime dispersers are the thrushes (Table 2), though other birds including woodpigeons will take fruit and may disperse seed; woodpigeons also take large numbers of unripe berries and may destroy 78% of the seed crop (Snow & Snow 1988).

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

7.07

No mechanism for external attachment.

7.08

(1)Roe deer will take some ripe fruit, so may act as dispersers also (Hélène Verheyden- Tixier, pers. comm.), as do martens (Trémolières et al. 1988).

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

8.01

Unknown.

8.02

(1)There does not appear to be any extended period of seed dormancy or the formation of a soil seed bank (Warr 1991; Kjellson 1992).

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

8.03

(1)In terms of chemical control of ivy, the foliage is resistant to 2,4-D and mildly resistant to 2,4,5-T in water, although the dormant shoot is susceptible to 2,4,5-T diluted in oil; the stump or stem may also be controlled with ammonium sulphamate in water (Fryer & Makepeace 1978). The systemic herbicides triclopyr amine and triclopyr ester are also effective control agents (Swearingen & Diedrich 2000). (2)Derr (1993) has shown that a 25% glyphosphate treatment coupled with cutting of the ivy's leaves to facilitate herbicide absorption will result in an almost 100% removal of ivy from the affected area. Neal and Skroch (1985) also have shown that timing of herbicide application is important, with herbicide application in March being most effective. Although herbicides can be effective in removing ivy, herbicide use introduces a potential environmental contaminant and is non discriminatory toward native foliage.

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648. (2)Biggerstaff, M. S. and C. W. Beck. 2007. Effects of method of English ivy removal and seed addition on regeneration of vegetation in a southeastern piedmont forest. American Midland Naturalist 158 (1) : 206-220.

8.04

(1)Cutting and grazing generally reduce the competitive abilities of ivy, and it shows low tolerance of fire when it does burn. However, being evergreen and with a relatively high water content, ivy is slow to burn and will not readily spread fire well.

(1)Metcalfe, D. J. 2005. Hedera helix L. Journal of Ecology 93(3): 632–648.

8.05

Unknown