Other Invasive Species We Treat

Yellow iris (Iris pseudacorus), also known as yellow flag or yellow flag iris, is a perennial aquatic plant that is native to Eurasia and North Africa. It was first introduced to Ontario in 1940 as an ornamental plant for ponds and water gardens but has since escaped cultivation and can now be found across Ontario in a wide variety of aquatic, semiaquatic, and terrestrial environments. In these environments this poisonous plant, whose sap can induce dermatitis, can form dense mats that displace beneficial native plant species and decrease local biodiversity. These mats can grow to such an extent that they clog irrigation channels and drainage ditches, and disrupt the function of stormwater management ponds. Left untreated, mats have the ability dry out wetlands, destroying the habitat available for wildlife. Yellow iris can most commonly be identified by its entirely yellow flower that has three drooping sepals that around three smaller upright petals. These flowers bloom between April and July and sit atop stems between 30 cm and 1 m tall that grow in groups of 2 to 10. The leaves of the plant fan out from the base and are flattened, up to 1 m long and 2 to 3 cm wide. However, when the flower is not present, yellow iris can often be confused with other wetland plants such as native purple/blue iris, cattails, and sweet flags.

Water soldier (Stratiotes aloides), also known as water pineapple, is a submerged, perennial aquatic plant native to Europe and Northwest Asia. Originally sold as an ornamental plant for water gardens, it is now primarily found in the Trent-Severn Waterway, the Black River, and Red Horse Lake within Ontario. Like many other invasive aquatic plants in Ontario, water soldier has the ability to form thick mats of vegetation. These mats, which appear during the summer months when the plant becomes buoyant, reduce water circulation, crowd out native vegetation, and have the potential to alter surrounding water chemistry. Water soldier mats are particularly hindering to recreational activities as the leaf edges are sharp and serrated, with the ability to cut individuals that come into contact with it. These sharp spines are a useful identification trait, normally sitting along narrow sword-shaped leaves that are bright green and up to 40 cm in length, arranged in a group that forms a rosette. In Ontario it is exceptionally rare to see water soldier flower, but if present the flowers will have three white petals and three white or green sepals.

Japanese knotweed (Fallopia japonica), also known as Asian knotweed, is a herbaceous perennial plant native to Eastern Asia. The first record of occurrence in Ontario traces back to 1901, when it was originally used as an ornamental garden plant and a form of erosion control. It has since rapidly spread across Ontario and can be found in wide variety of habitats ranging from the edges of buildings and roadsides in urban centres to riversides and wetlands in the wild. In this wide variety of settings, Japanese knotweed uses its particularly vigorous root system to break apart asphalt, concrete, and building foundations, or to rapidly outcompete neighbouring plants and form dense thickets that degrade local wildlife habitats. It is often mistaken for bamboo, having a smooth, semi-woody stem with a hollow interior. However, it can be differentiated through the reddish-purple colouring that can be found along its stems and its large, ovate leaves that range between 3-6 inches in length and 2-5 inches in width.

Common Buckthorn (Rhamnus cathartica), also known as European buckthorn is a tree or small shrub native to Eurasia. It was originally introduced in the 1880s to serve as an ornamental shrub for gardens and a windbreak along fencerows to protect agricultural land, but by the early 1900s it had already become widespread. An aggressive spreader, common buckthorn can survive in a wide range of soil and light conditions, forming dense thickets that smother most underlying vegetation. These thickets alter the local soil nitrogen levels, creating better conditions for their own growth while discouraging the growth of native plants. Common buckthorn also has the ability to harbor oat crown rust fungus and soybean aphid, two pests that reduce the yield of agricultural crops. It is often the first shrub or tree to sprout leaves in the spring and the last to drop its leaves in the late fall. These dark green leaves, which have finely toothed edges, are commonly between 2.5 and 6 cm long and grow on branches and twigs that end in a short, sharp thorn. Clusters of small, berry-like fruit can be found on trees and shrubs in late summer and early fall that are green when immature and black when fully developed, with a deep and narrow groove on the back. Common buckthorn is most often observed between 2 or 3 m in height, but is known to reach up to 7 m, and with small but prominent lenticels visible across its bark.

Goutweed (Aegopodium podagraria) has gained notoriety for its rapid spread and ability to outcompete native vegetation. Initially introduced as an ornamental plant, goutweed has become a nuisance in various regions due to its aggressive growth and tenacious nature. Goutweed is recognized by its distinctive, deeply divided leaves that resemble parsley or celery leaves. The leaves are bright green and grow in clusters. In summer, it produces small white flowers arranged in umbrella-like clusters. Originating in Europe and Western Asia, goutweed has become invasive in multiple areas. It is often found in disturbed habitats, gardens, and along roadsides. Once established, it can quickly spread and dominate the surrounding area. Goutweed is known for its ability to form dense ground cover, outcompeting native plants for resources such as sunlight, water, and nutrients. Its rapid growth and extensive root system make it difficult to control. Goutweed’s invasive nature can disrupt local ecosystems and threaten native plant species. Its presence can also hinder the growth of desired garden plants by competing for resources. Goutweed spreads through both seeds and underground rhizomes, making it particularly resilient and challenging to eradicate. Effective management often involves a combination of mechanical removal, repeated mowing, and herbicide application. However, control can be difficult due to its ability to regenerate from even small root fragments. Addressing goutweed infestations requires diligent monitoring and control efforts. Early detection and intervention are key to preventing its widespread establishment. Invasive plant species like goutweed underscore the importance of responsible gardening practices and raising awareness about the potential ecological impacts of introducing non-native plants into new environments.

Garlic Mustard (Alliaria petiolata) is an invasive plant species native to Europe that has become a significant ecological concern in many regions. Initially introduced for culinary and medicinal purposes, garlic mustard has spread rapidly and is now recognized as a threat to native plant communities and ecosystems. Garlic Mustard is characterized by its distinctive heart-shaped leaves with scalloped edges. The leaves emit a garlic-like odor when crushed, which is how the plant gets its name. It produces small, white four-petaled flowers in clusters at the top of the stems. Garlic Mustard is known for its aggressive growth and ability to outcompete native plant species. It releases chemicals into the soil that inhibit the growth of other plants, making it difficult for native flora to thrive. Its rapid spread can disrupt local ecosystems by reducing plant diversity and altering nutrient cycling. The invasive nature of garlic mustard can have cascading effects on ecosystem health. It can displace native wildflowers, which in turn affects pollinators and other wildlife that rely on them for food and habitat. Garlic Mustard reproduces by both seeds and roots, allowing it to spread quickly and efficiently. Its seeds are dispersed over relatively long distances, contributing to its invasive nature. Management efforts often involve manual removal, cutting before seed production, and the use of herbicides in targeted areas. Preventing the spread of garlic mustard is crucial. Avoiding the introduction of the plant to new areas and practicing responsible gardening are essential steps in minimizing its impact.

Invasive Wild Parsnip (Pastinaca sativa) is a plant species that has become a concern due to its aggressive growth, potential harm to humans, and negative impact on native ecosystems. Originally introduced as an ornamental plant and for its edible root, invasive wild parsnip is now recognized as a noxious weed in many areas. Invasive wild parsnip is characterized by its tall, erect stem that can grow up to several feet in height. It produces flat-topped clusters of small yellow flowers during its flowering season. The leaves are divided and fern-like in appearance. Invasive wild parsnip is found in various habitats, including roadsides, fields, meadows, and along waterways. It has spread to North America from its native Europe and Asia, and its presence is now documented in many states and provinces. Wild parsnip is known for its rapid and robust growth, outcompeting native vegetation in open areas. It can form dense stands that dominate landscapes and crowd out native plants. One of the significant concerns with invasive wild parsnip is its potential harm to humans. The plant contains toxic compounds that, when combined with sunlight, can cause skin reactions known as phytophotodermatitis. Contact with the sap and subsequent exposure to sunlight can lead to painful blisters and skin discoloration. Control measures often involve mechanical removal, mowing before flowering, and the application of herbicides in targeted areas. Due to the potential skin hazards, caution is necessary when handling the plant.

Invasive honeysuckle refers to several non-native species of the honeysuckle plant (genus Lonicera) that have become a concern due to their aggressive growth, negative impact on native ecosystems, and displacement of native plant species. These invasive honeysuckle species are often introduced for ornamental purposes but can quickly become problematic when they escape cultivation and spread into natural areas. Invasive honeysuckle species typically have fragrant, tubular flowers that range in color from white to pink, red, or orange. They produce pairs of opposite leaves and, in some cases, bright red or orange berries. Invasive honeysuckle species are known for their rapid growth and ability to form dense thickets. They often leaf out earlier in the spring and retain their leaves longer in the fall compared to native vegetation, giving them a competitive advantage. This can lead to the displacement of native plants and alter the structure and composition of ecosystems. Their dense growth can shade out native plants, reducing biodiversity and altering habitats for native wildlife. In addition, some invasive honeysuckle species produce berries that are consumed by birds, but these berries offer lower nutritional value compared to native berries, potentially affecting bird populations. Preventing the spread of invasive honeysuckle involves responsible landscaping practices and raising awareness about the potential ecological impacts. Restoration efforts focus on removing invasive honeysuckle and promoting the recovery of native plant communities.

Japanese Barberry (Berberis thunbergii) is a non-native shrub that has become a concern due to its aggressive growth, negative impact on native ecosystems, and potential association with increased tick populations. Originally introduced as an ornamental plant in 1870, Japanese barberry has escaped cultivation and established itself in various North American habitats. This invasive is characterized by its thorny branches and small, oval leaves that are typically green, but can turn shades of red or purple in the fall. It produces small, bright red berries that persist through the winter. Japanese barberry is found in a range of habitats, including forests, woodlands, fields, and disturbed areas. It is native to Japan and has been widely planted as an ornamental shrub in North America, where it has become invasive in many regions. Japanese barberry is known for its ability to form dense thickets that crowd out native vegetation. Its thorny branches provide shelter for small mammals, which can contribute to the spread of ticks that carry Lyme disease. Invasive Japanese barberry’s leaf litter creates a favorable environment for ticks by providing humidity and protection from predators. Japanese barberry spreads by seeds, which are dispersed by birds and mammals that consume the berries. Control measures often involve mechanical removal, cutting, or herbicide application. Early detection and control are essential to prevent further spread.

Dog-Strangling Vine (Cyanchum rossicum) is a non-native vine that grows aggressively, wrapping itself around trees and other plants. Dog-Strangling Vine (DSV) outcompetes native flora by forming dense thickets that crowd out other vegetation. Originally introduced to North America as an ornamental plant, DSV can now be found throughout Ontario, Quebec, and some of the North-East United States. DSV offers no ecological value to wildlife and therefore displaces many species. Deer and other browsing species avoid DSV, which can increase the pressure these herbivore species have on native species. DSV also displaces bird habitats and does not host any insect groups. This invader also has negative impacts on forestry and agriculture, as its presence in woodlots and fields reduces the available nutrients for the desired harvestable plants. DSV’s dense growth can also impede recreational activities as its dense growth can be found crossing hiking trails and infringing upon campgrounds. Small populations of DSV can be controlled by digging up the roots and disposing of the plant responsibly. Larger infestations often require a combination of chemical control. DSV should be allowed to dry-out completely before being disposed of or moved off-site.