dry-moist ravine, shaded conditions, rich soil
There are many native Asters in Ontario and distinguishing one from another can be very difficult, especially in a ravine setting where growth habit can differ due to fluctuations in soil moisture and sunlight penetration through the tree canopy.
I believe the Aster in your photo is a Eurybia macrophylla or commonly called Large-leaved Aster. These plants are widespread in Ontario forests and ravines. See the link below for more information on this lovely Ontario Native Wildflower.
Hope this helps.