Invasive Species

SAWIG is actively involved in invasive species management, identification and monitoring. Not only is our watershed coordinator a member of the PEI Invasive Species Council, but we also actively survey for and manage invasive species within our watershed boundaries in the late spring and summer months! 

Not sure if you've spotted an invasive species? Mark your location on iNaturalist or EDDMapS and we’ll check it out!  

What's an Invasive Species?

Canada has a wide variety of species of plants and animals; the biodiversity of our country is amazing! Unfortunately, not all of these species are native to our area; in fact, there are some that should not live here at all!

To put it simply, an invasive species is...

... Any species that is not native to an area and threatens the environmental, economic or social health of the area.(PEI Invasive Species Council, 2012)

Invasive species can be plants OR animals.

How Do Invasive Species Get Here?

Some of these plants and critters catch a ride from other parts of the country (or the world) through various means; some mooch a lift on humans, in cargo, on the bottom of boats or in ship ballasts. Invasive species can pose serious risks to native flora and fauna.

Invasive species: Purple Loosestrife / Photo: Mike Ogden

Why are Invasive Species an Issue?

Once a species is removed from its native area and grown elsewhere, it may no longer have to face any predators or other threats which would normally keep the population in check. This means a particular species is free to quickly reproduce, grow and take over entire areas that were once populated by native plants or animals. For this reason, invasive species often outcompete native species for essential resources such as sunlight and nutrients.

What are the MOST Invasive, Invasive Species?

While all invasive species harm the environment in some form, the PEIISC has a prioritized list of the invasive species residents of Prince Edward Island should watch out for. Here is a quick introduction to some notable species:

Yellow Flag Iris

Yellow Flag Iris is an ornamental planet which originates in Europe, Northwest Africa and Western Asia. It grows in moist ground and frequents ditches, wetlands, and around waterways. You can identify Yellow Flag Iris by its sword shaped leaves which range from 0.5m-1.5m long and 1-3cm wide with a raised ridge in the middle of the leaf.

Control Measures

The PEISC recommends completely digging the plant from the ground. Care must be taken to remove all aspects of the plant, roots, rhizomes etc. as the plant will grow again from the remainder. Mowing or cutting has been proven effective as it inhibits photosynthesis eventually killing the plant. In regards to both of these containment efforts the site must be monitored annually to ensure the plant has been eradicated.

Yellow Flag Iris 

Wild Cucumber

Wild Cucumber grows in most areas across PEI, alongside trails, in fields or in forest areas. Wild cucumber is a vine that grows on other shrubs and trees and can choke out smaller plants. It is easily identified by its soft spiky fruit, as well as its leaves with 5 lobes and a heart-shaped base.

Control Measures

Mowing or cutting the plant back in the spring is the best way of ensuring plant mortality.

Leaves of Wild Cucumber 

Scotch Broom

Scotch Broom grows in open habitats such as fields, meadows and yards. It has an extensive root system and becomes very difficult to eradicate once established. Scotch Broom originated from Europe and was brought over originally as an ornamental plant. It has also been used as a coffee alternative and for medicinal purposes. Scotch Broom is identifiable by its yellow, pea-like flowers which bloom from May to June. The leaves near the base of the plant contain 3 leaflets, and it has a woody, angled stem.

Control Measures

Scotch Broom is difficult to manage as its seeds can remain viable in the soil for up to 30 years (yikes!). Digging is only an option for small infestations. The best management strategy is to cut the plant to ground level and cover with thick black plastic to 'smother' future growth.

Flower and leaves of Scotch Broom 

Purple Loosestrife

Purple Loosestrife grows along waterways, choking out native plants and destroying natural environments. It can be identified by its purple to pink flowers (5-7 petals each), which grow on “spikes” that are 10-40cm long. The flowers of purple loosestrife bloom from July to September.


Digging is the most effective method of eradicating infestations of Purple Loosestrife. When digging, care should be taken to remove as much of the root system as possible to limit regrowth.

Purple Loosestrife 


Periwinkle can be found at ground level in forests and over-shaded areas. It grows and spreads rapidly, choking out most native ground cover plants. Periwinkle can be identified by its glossy, evergreen leaves and its pale blue flowers which are 3cm wide and have 5 petals. Periwinkle flowers bloom from May until June.


To remove periwinkle, dig up the whole plant. Make sure that the whole root system has been removed from the ground as any remaining pieces of root will be able to grow into a new plant. In order to do this most effectively, remove plants when soil is damp or soft. 

Want to learn more about invasive species?

Visit the PEI Invasive Species Council's website for up-to-date information on all things invasive species.

SAWIG 2023 - Invasive Species Removal Achievements

SAWIG managed several invasive species that threaten our watershed's ecological balance. Summer staff removed a large section of Purple Loosestrife along the Trans Canada Highway, cleared multiple locations around Kelly’s Pond and in Pownal of Himalayan Balsam, continued management of a patch of Garlic Mustard, began removing and managing a large coastal patch of Japanese Knotweed near Cotton Park, and removed a large quantity of watercress and Bittersweet Nightshade from Jack’s Creek.

Total Area

In total, SAWIG surveyed 1010.59 m² of land during our invasive species removal efforts. 

Total Weight

All invasive plants that were removed were brought to an incinerator to prevent any regrowth from removed plant fragments. In total, we brought 1170 kg of invasive plants to the incinerator.