Milkweed (Asclepias)

Riding Mountain National Park


Do you recognize the plant in this picture? It’s milkweed! This plant has an extremely important role to the play in the survival of the Monarch butterfly, which is now considered a species at risk and was recently reassessed by COSEWIC (Committee on the State of Endangered Wildlife in Canada) as endangered.

Monarch caterpillars feed exclusively on the leaves of the milkweed plant and the availability of this plant is crucial to the monarch’s survival. Unfortunately, it is becoming increasingly less plentiful due to habitat destruction, which in turn has drastically decreased monarch numbers.


Monarchs could be legally listed as endangered by SARA (Species at Risk Act) as early as winter 2018. It is anticipated that milkweed will be identified as the monarch’s residence and included in the critical habitat identification for this species in the future.

Parks Canada has a role to play in the conservation of the monarch, milkweed, and other pollinator species. In order to implement conservation measures, we need to find out where the milkweed and monarchs are so we can get a rough idea of their distribution in Riding Mountain National Park.

Here’s how you can help:

The best approach for observing and reporting monarchs and milkweed is for staff and visitors to take photos with their phone while their location services are enabled (or mark the point with a GPS) and submit the observation to iNaturalist via their app or online: The result is a documented record that Manitoba Conservation Data Centre can access and use for species conservation and evaluation.

There are two native species of milkweed in RMNP:

  • Oval-leaved Milkweed - Asclepias ovalifolia
  • Showy Milkweed - Asclepias speciosa 

We are past the peak flowering period for both but they may persist until August or later.

So far these are the only locations documented for milkweeds in the park:

We are hoping that with your help, we can fill in the map a little bit more!

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