Species at Risk

Mingan Thistle

What is the Mingan Thistle?

The Mingan thistle (Cirsium scariosum) is a member of the Aster family (Asteraceae). Pale green in colour and covered with thorns, it is hard to distinguish from other species until it is mature (flowering). Indeed, for most of its lifespan, it is only made up of basal leaves. In the first year, the seedling has 3 leaves on average and rarely extends more than 5 cm in diameter. The plants remain in a vegetative state for several years, increasing the number of leaves from one summer to the next. These basal rosettes reach a diameter of between 0.7 and 111.3 cm. Then, between the ages of 4 and 14 years, the Mingan thistle flowers once only at about mid-July, and then dies. At this stage, it has a stem (between 2.6 and 74.5 cm tall) with a bunch of pale purple to pink capitates at its end. At maturity, the seeds are topped by aigrettes or feathery crowns that are scattered by the wind. This is their only means of spreading.

Where is Mingan Thistle found?

The most likely hypothesis to explain the Mingan thistle’s geographic distribution is that it could be a remnant of Western flora that established itself in the area following the last ice age.

 

In Quebec, the Mingan thistle is found only in the Mingan Archipelago National Park Reserve of Canada (MANPRC) where it grows mainly along the littoral zones surrounding the islands. More accurately, it grows on only four of the park’s islands. Elsewhere in Canada, the species can be found only in a small area in southern Alberta and British Columbia; it can be found among other places in the Waterton Lakes National Park of Canada. The two ranges are therefore at a distance of 3500 km from each other.