Grosse Île and the Irish Memorial National Historic Site of Canada

Natural Heritage



Diversified Vegetation

Since the 19th century, botanists have been fascinated by the extraordinary vegetation on Grosse Île. The famous Brother Marie-Victorin reported in 1935 “that by its geographical location, Grosse Île is the front of penetration for the estuarial flora in the maritime section and vice-versa.” This location provides interesting ecological conditions for the development of vegetation in this part of the Saint Lawrence.

Small island

Centrally located in the Laurentian estuary, Grosse Île is part of the Isle-aux-Grues archipelago. It has a surface area of 2.2 km2: 2.7 km long by 800 m wide.

Diverse habitats

Despite its small size, Grosse Île features three main habitats.

Grosse Île shoreline Grosse Île shoreline
© Parks Canada / E. Le Bel

First, the coastline, with its grassy bays and rocky shoreline, makes up about 25% of the island’s surface. Subjected to strong tides of close to 7 m and lightly salted water, the coastline is populated with groups of American bulrush.


Marsh Marsh
© Parks Canada / E. Le Bel

Second, the island’s wetland and luxurious vegetation covers about 11% of its surface. This habitat, with its rich and water-logged soil, is home to an uncommon marriage of speckled alder and skunk cabbage.


Forest Forest
© Parks Canada / E. Le Bel

Lastly, a forest covers more than 70% of the island and contains more than 25 species of trees, especially balsam fir, red maple and Canadian hemlock.


Many rare plants

The ecological and physical conditions of these habitats result in a rich and Diversified Vegetation of close to 600 species, including 24 plants considered rare in Quebec.

Grosse Île’s rare plants are vulnerable since they are generally found in small communities confined to constricted areas, or grow at the limit of their distribution area. Some rare plants on Grosse Île can be found in wooded areas, such as the male fern. However, the majority of rare plants, such as the Victorin’s gentian, inhabit the shoreline where most of these grow exclusively in the St. Lawrence estuary.

Advice when visiting

To appreciate and preserve this unique vegetation, we encourage you to use the groomed trails and avoid walking in the vegetation along the shoreline and in the woods. This way you can enjoy these wonders of nature without further endangering them.