Unexpected

After the pool I went to Isel Park to take a blip of the bare winter trees for MonoMonday.  Walking around the path I didn't expect to come across a large group of Monarch Butterflies gathered on these white flowers.   I have no idea what the shrub is called.  It is about three meters tall with large leaves like the Gunnera  plant.  There would have been 20 to 30 butterflies fluttering around it.  I am assuming the butterflies are overwintering in the park.