Looks like white-flowered hardy Ageratum, Conoclinium coelestinum 'Album'. It's a perennial rather than a shrub.

Or eupatorium chocolate without the colored leaves. Mine is blooming now and gets about 3' by 3'.

This post was edited by mnwsgal on Wed, Oct 15, 14 at 1:13

deffo a eupatorium...i also thought conoclinum coelestinum but they usually top out at around 2feet.

Thanks for the help everyone.

I am not sure how long it has been in bloom but it looks beautiful right now...lots of pollenators on it also....a very happy looking plant.

Given that it is in full bloom in mid October, I can imagine years when it might have fallen to an early October frost :(.

Mine continues to bloom through light frosts without any damage. I cut the blooms off before they fully go to the fluffy seed stage to keep reseeding to a minimum but leave the foliage which turns light yellow. There are several plants in the clump with some blooming a bit later making for a long bloom display.