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Invasive Plants You May Recognize

Simply put, invasive means "out-of-control". Invasives are immigrant species brought from an outside ecosystem or environment. In its natural environment, there are natural factors or enemies that maintain the growth or spreading of any species. When that species is introduced to a new environment or ecosystem, there is likely no natural control features. Allowing the species (plant or animal) to take over an area with little effort.

Some more commonly known invasives would include; Zebra Mussels (Dreissena polymorpha), Purple Loosestrife (Lythrum Salicaria), and Giant Hogweed (Heracleum mantegazzianum)

Urban Invasives

Urban invasives are very common. They are plants that most garden centers will have available for purchase but are difficult to control once planted. Most gardens contain invasives without even knowing it.

Lily-of-the-valley (Convallaria majalis) is an urban invasive plant. It does very well in our zone (Zone 3 - 4 CDN) but can be difficult to keep in an isolated area. Lily-of-the-valley prefers shaded areas and is a tuberous plant. This plant is also poisonous but when dried, is used in herbal remedies.

If Lily-of-the-valley is one of your favorites, make sure to maintain the planted area and remove access plants to prevent unwanted spreading.

Periwinkle (Vinca minor) is a beautiful perennial vine. Shade loving and can grow anywhere. Even with its deep green foliage and range of available colored flowers, it is still very invasive. Able to grow several metres per year, this plant can quickly become out of control.

The best control method for periwinkle is continuous maintenance throughout the growing season. There are no special pruning techniques required. Just grab the vine and cut. You can cut it back safely to 6" from the main root.

Bishops Goutweed aka Bishop Weed, Snow-on-the-mountain (Aegopodium podagraria variegatum) is usually recommended as a ground cover for hard to grow areas. It works great! So great that your whole garden will be covered with it in no time. This invasive reproduces by seed that can be carried in the wind and by rhizomes (spreading, underground roots that send new stokes up).

This plant is deer and rabbit resistant. To prevent seeding, cut the flower heads off as soon as you notice them.

The best control is not planting it at all. If your garden does contain this hostile plant, some sprays may be effective but you're likely going to need to do some heavy digging to get all those roots and runners to completely remove it. 

Wild Invasives

When most people think of invasive species, wild species are considered. Most wild invasives started in a garden. A new, interesting plant type is purchased and planted. Flowers bloom and seeds form. Seeds are dispersed by the plant and voila, the spread of an invasive.

Dog-Strangling Vine (Cynanchum rossicum)(refered to as DSV) was introduced in the mid-1800's as a garden plant in the northeastern United States. It is know spreading through Ontario like a plague. Growing easily 2 metres a year, this vine wraps itself around trees and other plants and literally strangles the it to death. Like most invasives, DSV starts its growing season earlier than our native species, suffocating and preventing native species growth.

Another extremely negative about DSV is its impact on the Monarch butterfly (Danaus plexippus) population. Similar in appearance to our native common milkweed (Asclepias syriaca), a required plant species for Monarch butterfly habitat, the butterflies mistake DSV for milkweed and lay their eggs under the leaves. The larvae do not survive, impacting the future of the Monarch species. 

Small clumps you may find in your garden, can be dug out when the plant is young. After the 2nd year, the roots are so established herbicides will be required to kill the plant. Multiple applications may be needed depending on the age and amount of DSV.

Ministry of Natural Resources PDF - Forest Health Alert - Dog-strangling vine -

European Common Reed (Phragmites australis subsp. australis) can be seen all over southern Ontario ditches and wetlands. This invasive provides little value to wildlife and chokes out native Cattails (Typha latifolia), which provide habitat for wetland wildlife.

Glyphosate herbicide seems to be the best control as the roots must be killed to prevent re-growth.

Make sure to check clothing and equipment for seeds when you have been in contact with this plant to prevent further spreading.

Ministry of Natural Resources - Terrestrial Invasive Species - 



Invasive Plant Species Assessment Working Group.2007.Periwinkle Vinca minor. [online]. dnr/files/Periwinkle.pdf.

Nature Hills Nursery. 2014. Bishop Weed. [online].

Ministry of Natural Resources. 2010. Ontario’s Forests. Dog Strangling Vine. [online].

Ministry of Natural Resources. 2013. Terrestrial Invasive Species. European Common Reed. [online].

Missouri Botanical Garden. 2014. Convallaria majalis. [online]. http://www.missouribotanical

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