Written By: Chris Aultman, Dylan Henry, Charlotte Leivo, Annika Young
There are four invasive groundcovers that are becoming an increasing concern in Canada and United States of America, for they are becoming better established within the natural environment: English Ivy (Hedera helix), Goutweed (Aegopodium podagraria), Lily of the Valley (Convallaria majalis), and Periwinkle (Vinca minor).
Common invasive groundcover species are Periwinkle (Vinca minor) and Goutweed (Aegopodium podagraria) originate from Eurasia. The two plants now grow in Southern Canada from British Columbia to Southern Ontario, as well as the West coast and East United States. The global distribution of the two invasive plants can be found on Figure 1 and the distribution of the plants in Ontario can be found on figure 2.
Lily of the Valley, Convallaria majalis, originates from Europe and Eurasia (shown in Figure 3). The species ranges from most States and some of Southern Canada (shown in Figure 2). They were brought to North America by settlers that used this plant for ornamental and medicinal purposes. It is highly toxic to animals, particularly the leaves and each plant has a different amount of toxin called convallatoxin. (Kaufman & Kaufman,2007).
English Ivy, Hedera helix, is an evergreen climbing plant native to Europe, western Asia, and northern Africa (Kaufman & Kaufman, 2007). English Ivy was introduced to North America as a decorative plant starting in the 1700s and is now considered an invasive species (Kaufman & Kaufman, 2007). It is found in 26 states in the United States, southern British Columbia, and southwestern Ontario and has also been introduced to South Africa, India, Australia, New Zealand, Brazil, and Mexico (Kaufman & Kaufman, 2007; Waggy, 2010).
Periwinkle is often found in open forests and around old home-sites as they were favoured by early European settlers for their medicinal properties. (Kaufman, Kaufman. 2012) These
plants can be found in soils that are: Silt loams, Clayey, loamy and sandy soils, and rocky sandy soils. (Stone. 2009) However, they prefer soils that are fertile and moist but can tolerate lowly fertile and moderately to well-drained soil site locations.(Stone, 2009) They further favour soils that are relatively shallow, 5.7-8.7 inches deep, and grow in soils of 5.7-7.2 PH levels. Periwinkle favours partial shade but is known to tolerate full sun and fully shaded areas. (Stone, 2009)
Goutweed is often found in moist sites, preferably sites that are moist and well drained within partial shade areas. (Waggy. 2010) These plants are tolerant of floodplains and
moisture contents that are 33.2-36.4%. Goutweed is known to be a nitrophilous species, meaning they are indicators of nitrogen rich soils but is more restricted by soil PH levels.
The PH levels they have been known to occur in is 3.1-9 within its native range in Europe. (Waggy, 2010)The soil they seem to prefer are: Sandy loam, silty loam, and sandy clay.
(Waggy, 2010) These species are highly tolerable of highly shaded area where the canopy layer is 90% and seem to prefer thin litter layers to spread. (Waggy, 2010)The areas they are known to first establish within are roadsides, forest edges and disturbed forest floors (Kaufman, Kaufman) before expanding vegetatively into areas that seed germination is not favourable.
Lily of the valley has adapted to grow in a wide range of soils that are acidic and alkaline.
(Vandepitte, De Meyer, Jacquemyn, Roldan-Ruiz, & Honnay, 2013) However, is mainly found within acidic soils in its native range and its non-native range in North America. They thrive within fertile and humic soils (Kaufman, Kaufman) with well drained moist soils. (Vandepitte, De Meyer, Jacquemyn, Roldan-Ruiz, & Honnay) Within its native range it is mainly found in ancient deciduous forest and naturalizes within similar forest types around the world. Studies suggests that it can tolerate coniferous forested sites with highly acidic soils as well as low light conditions but does not perform well under these conditions. (Verstraeten, Baeten, De Frenne, Thomaes, Demey, Muys, & Verheyen. 2014) Further indicating that they can thrive within mix-forested, Carolinian and boreal forests in Canada.
The preferred habitat of English Ivy in its native range is floodplains with moist, nutrient-rich substrates (Schnitzler & Heuzé, 2006).
Its preferred hosts in this environment are large and isolated trees that provide greater surface area for attachment and increased exposure to sunlight (Castagneri, Garbarino, & Nola, 2013). In North America, English Ivy prefers moist areas with full to partial shade but can also tolerate drought (Kaufman & Kaufman, 2007). It has been noted to thrive in disturbed and fragmented forests (Kaufman & Kaufman, 2007; Londré & Schnitzer, 2006). English Ivy is capable of growing in Canadian Hardiness Zones 4a to 8b (Pascoe, 2017).
Organisms can generally be divided into two broad categories of reproductive strategy: r-selection and K-selection. R-strategists have high population growth rates and typically colonize new or disturbed areas, while K-strategists favour efficient use of resources and are typically found in areas where populations are near carrying capacity (Molles & Cahill, 2014). Most species of invasive plants would be expected to be r-strategists. However, despite its preference for colonizing disturbed areas, English Ivy displays two traits associated with K-strategists: longevity and parental investment. English Ivy can live for many decades. Schnitzler and Heuzé (2006) found a specimen in northeast France that was at least 66 years old. Its seeds, rather than being wind-borne, are carried in fruits (Kaufman & Kaufman, 2007). In addition, English Ivy appears to be capable of establishing or persisting in late-successional as well as disturbed communities (Waggy, 2010). English Ivy is therefore closer to being a K-strategist than an r-strategist. Its pattern of survivorship also supports this conclusion. English Ivy can spread via runners, bird-dispersed seeds, or cuttings in contact with earth (Kaufman & Kaufman, 2007).
The primary method of reproduction for Vinca minor and Aegopodium podagraria are underground runners from rootlets (Kaufman, Kaufman, 2007). Both of the species rarely repopulate from seeds. The seeds from Goutweed need very specific conditions to survive after germination, the requirements are recently disturbed soil and a sunny location (CVC, 2017) Both Periwinkle and Goutweed have attributes that make them r-strategist species. The r-strategists attributes the species have are rapid growth rate, and frequent reproduction through the runners and quick to maturity.
Lily of the valley, Convallaria majalis propagates by two methods. During warm months the plant sends out underground stems called rhizomes, which form new upright shoots called stolons. In the spring these grow into new leafy shoots that still remain connected to the other shoots under ground, and often form large colonies. It also produces a small, white, sweetly scented flower that produces a small orange-red berry. The berry contains a few large whitish to brownish colored seeds that dry to a clear translucent round bead. Majalis cannot self fertilize and it is self-sterile, if there are not two colonies available to cross pollinate the plant will not be able to seed. (Chace & Coover, 2012).
The survivorship of many invasive species are type three, with high mortality at seedling stage of life followed by high rate of survival among the fully grown (Molles, Cahill, 2014) The type three curve fits the survivorship of Periwinkle, Goutweed and Lily of the Valley because of the low chance of seedling for the plants to germinate. However through the reproductive strategy of runners there is a higher chance of surviving due to the main body being established, Figure 3 shows a survivorship curve representing the three survivorship types based on organisms survived over time.
The germination rate of English Ivy seeds is near 100%, especially with the pulp removed via digestion by birds (Biggerstaff & Beck, 2007). Low juvenile mortality suggests either a Type I or II survivorship curve depending on whether mortality rates are greater (Type I) or the same (Type II) among older individuals (Molles & Cahill, 2014).
Dispersal and Vectors
The primary vector for Common Periwinkle, Goutweed and Lily of the Valley would be humans; Humans either improperly dispose of the garden waste produced by these plants or they plant these groundcovers due to the beautiful flowers produced, easy maintenance and edibility. (Kaufman & Kaufman. 2007) Because of the rhizomes on the roots, the plant can easily be establish in the compost. (CVC, 2017) Due to these plants being widely distributed and sold by plant nurseries and lack of education on the impacts they have ecologically, consumers may plant them on their property were the invasive plants can easily escape into the surrounding environment.(Darcy & Burkart. 2002). Common periwinkle is known to be dispersed throughout its native range by the means of ants (Stone, 2009), it is currently unknown whether or not this occurs in North America. Due to the toxicity of lily of the valley no known species disperse the seeds over a long distance. Goutweeds main dispersal agent is gravity and the wind pushing the seeds a small distance, it is currently unknown if animals aid in the dispersal of ribbed seeds that could adhere onto fur. (Waggy, 2010) Due to the lack of seeds that these plants produce, this prevents any major dispersal over varying distances, however if unchecked the plants can overtake a substantial area through the underground root systems. English Ivy and other invasive groundcovers are still planted in gardens, where they can grow into natural areas(Ontario’s Invading Species Awareness Program, n.d.). The seeds of English Ivy can also be dispersed by birds (Kaufman & Kaufman, 2007).
The juvenile and adult stages of English Ivy differ greatly in growth form, reproductive capacity, and leaf shape (Castagneri, Garbarino, & Nola, 2013). These differences are summarized in Table 1. The leaves of the adult form have greater total photosynthetic capacity than the leaves of the juvenile form. However, the leaves of the juvenile form are better at adapting to changing light levels due to greater phenotypic plasticity (Bauer & Thöni, 1988). English Ivy has some medicinal uses and is capable of causing contact dermatitis (Kaufman & Kaufman, 2007; Paulsen, Christensen, & Andersen, 2010).
Table 1: Comparison of juvenile and adult Hedera helix. Adapted from Castagneri, Garbarino, & Nola, 2013.
|Leaf Shape||Palmately lobed||Unlobed, oval-shaped|
Convallaria majalis and Aegopodium podagraria are both non-native to North America and have no known predators in their introduced habitats. Vinca minor , however has been noted in Illinois to have one known predator, which is White-tailed deer. One consideration of these species is if they are being removed through excavation the entire root mass and all runners should be removed to prevent the organisms from re-establishing. All species have been known in the past to be used for medicinal and ornamental purposes. Lily of the Valley is toxic to most animals.
Bauer, H., & Thöni, W. (1988). Photosynthetic light acclimation in fully developed leaves of the juvenile and adult life phases of Hedera helix. Physiologia Plantarum, 73(1), 31-37. doi:10.1111/1399-3054.ep12975682
Biggerstaff, M. S., & Beck, C. W. (2007). Effects of English Ivy (Hedera helix) on Seed Bank Formation and Germination. American Midland Naturalist, 157(2), 250-257.
Castagneri, D., Garbarino, M., & Nola, P. (2013). Host preference and growth patterns of ivy (Hedera helix L.) in a temperate alluvial forest. Plant Ecology, 214(1), 1-9. doi:10.1007/s11258-012-0130-5
Chace, T. D., & Coover, C. (2012). The anxious gardener’s book of answers. Portland, Or.: Timber Press.
Chace, T.D. (2013) How to Eradicate Invasive Plants. Portland Oregon: Timber Press Inc.
Credit Valley Conservation, (2017) Invasive Plants (Aquatic & Terrestrial), Your Land and
Water, retrieved on January 26, 2017, from http://www.creditvalleyca.ca/your-land-water/tree-planting-and-habitat-restoration-services/invasive-species/invasive-species-spotlights/invasive-plants-spotlight/
Darcy, A.J., & Burkart, M.C. (2002). Allelopathic Potential of Vinca minor, an Invasive Exotic Plant in
West Michigan Forests. Bios, 73(4), 127-132. Retrieved fromhttp://www.jstor.org/stable/460864
D’Hertefeldt, T., Enestrom, J., & Pettersson, L.B. (2014) Geographic and Habitat Origin Influence Biomass Production and Storage Translocation in Clonal Plant Aegopodium podagraria. Plos ONE, 9(1), 1-8
EDDMapS. (2017) Early Detection & Distribution Mapping System. The University of Georgia –
Center for Invasive Species and Ecosystem Health. Available online at http://www.eddmaps.org/; last accessed January 25, 2017.
Garske, S. Schimpf, D. (2005) Fact Sheet: Goutweed. Plant Conservation Alliance’s Alien Plant Working Group. Retrieved from http://www.nps.gov/Plants/aliean/Fact/aepol.htm
iNaturalist, (2017) Lesser Periwinkle (Vinca minor) map/about, iNaturalist.ca, retrieved on January 27, 2017, from http://inaturalist.ca/taxa/55844-Vinca-minor
Kaufman, S.R., & Kaufman, W. (2007). Invasive plants. Mechanicsburg, PA: Stackpole Books.
Londré, R.A., & Schnitzer, S.A. (2006). The distribution of lianas and their change in abundance in temperate forests over the past 45 years. Ecology, 87(12), 2973-2978. Retrieved from http://isites.harvard.edu/fs/docs/icb.topic941093.files/Week%205.%20Vine%20Distribution%20Temperate%20Forests%20%20Ecology.pdf
Molles, M.C., & Cahill, J.F. (2014). Ecology: concepts and applications. Canada: McGraw-Hill Ryerson.
OISAP, (2017) Invasive Ground Cover, Ontario’s Invading Species Awareness Program, retrieved on January 27, 2017, from http://www.invadingspecies.com/invaders/plants-terrestrial/invasive-ground-covers/
Ontario’s Invading Species Awareness Program. (n.d.). Grow me instead: beautiful non-invasive plants for your garden. Retrieved from http://www.invadingspecies.com/invaders/plants-terrestrial/invasive-ground-covers/
Pascoe, M. (2017).Hedera helix ‘Thorndale’ (Thorndale English Ivy). Retrieved from http://www.canadaplants.ca/display.php?id=89
Paulsen, E., Christensen, L. P., & Andersen, K. E. (2010). Dermatitis from common ivy ( Hedera helix L. subsp. helix) in Europe: past, present, and future. Contact Dermatitis (01051873), 62(4), 201-209. doi:10.1111/j.1600-0536.2009.01677.x
Schnitzler, A., & Heuzé, P. (2006). Ivy (Hedera helix L.) dynamics in riverine forests: Effects of river regulation and forest disturbance. Forest Ecology And Management, 23612-17. doi:10.1016/j.foreco.2006.05.060
Stone, K.R (2009) Vinca Major, V, Minor. In: Fire Effects Information System [Online]. U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Retrieved from http://www.fs.fed.us/database/feis/plants/vines/vinspp/all.html
Vandepitte, K., De Meyer, T., Jacquemyn, H., Roldan-Ruiz, I., & Honnay, O. (2013). The Impact of extensive clonal growth on fine-scale matting patterns: a full paternity analysis of a lily-of-the-valley population (Convallaria majalis). Annals of Botany, 111(4), 623-628
Verstraeten, G., Baeten, L., De Frenne, P., Thomaes, A., Demey, A., Muys, B., & Verheyen, K. (2014). Forest herbs show species-specific responses to variation in light regime on sites with contrasting soil acidity: An experiment mimicking forest conversion scenarios. Basic and Applied Ecology, 15316-325. doi:10.1016/j.baae.2014.05.002
Waggy, M.A. (2010). Hedera helix. Retrieved from https://www.fs.fed.us/database/feis/plants/vine/hedhel/all.htm
chery. (2006, October 16). Hedera helix clinging. Retrieved from https://commons.wikimedia.org/wiki/File:Hedera_helix_clinging.jpg
Husthwaite, R. (2009, April 23). Survivorship curves. Retrieved from https://commons.wikimedia.org/wiki/File:Survivorship_Curves.jpg
Kenraiz. (2008, November 15). Hedera helix native range. Retrieved from https://commons.wikimedia.org/wiki/File:Hedera_helix_area_kz1.png
United States Department of Agriculture. (n.d.). Hedera helix North American range. Retrieved from http://bioweb.uwlax.edu/bio203/s2009/hitchins_abby/Habitat.htm
Peters, K. (2005, July 15). Aegopodium podagraria blatt. Retrieved from https://commons.wikimedia.org/wiki/File:Aegopodium_podagraria_blatt.jpg
Zell, H. (2009a, April 14). Vinca minor 001. Retrieved from https://commons.wikimedia.org/wiki/File:Vinca_minor_001.JPG
Zell, H. (2009b, April 29). Convallaria majalis 0001. Retrieved from https://commons.wikimedia.org/wiki/File:Convallaria_majalis_0001.JPG