What is it!

I need some help to ID this perennial, it is growing in a planter seldom watered and flowers around august. It grows to exactly the same size every year and does not spread. Growing in full sun and the very cold Canadian winters does not seem to bother it. Does anyone one have any idea what it is.

 

Can you get a close-up photo?

 

I will check my data base to see if I have a closer pic I was leaning toward dianthus or coreopsis but I'm not convinced on either maybe a perennial aster?

 

What is it?

This is as close as I got.

 

I don't think it's any of those.

 

Thanks; unfortunately not a plant I recognise either.

 

One of the dwarf Vernonias, such as Vernonia lettermannii.