Halifax Planter Box

Planter box in Halifax; Photo © Karen Thiessen, 2014

I spotted this planter with its colourful painted branches on Gottingen Street in Halifax's North end this summer. The purple branches and flowers are a nice complementary contrast to the yellow building. Does anyone know what the flowers are (aside from pretty and purple)? 
Update: Diana tells me that the pretty purple flowers are Verbena bonariensis. Thanks Diana!