I've a feeling it's a type of Artemisia, but can't remember which one.....

It looks similar to the Artemesia limelight I have / had. So please becarefukl where you plant it. I bought a 6" pot of a lovely leafed plant that I put in one of my borders, It behaved it self very well the following year, it grew to a height of about 4' but only doubled in size at the root ball. The following year, it had taken over most of the border (about 9' x 12'), i dug it out, the om split it into sections and dotted it around his field. It is surviving the thick grass and weeds. It wasn't happy in dappled shade in the woods, so it didn't survive there. I am still digging out sections that are growing from tiny bits of root left in the border and that is about 4 yrs ago, i dug it out.

So another thug to add to the list!

this one should be at least in the top ten of the list of the most thuggish.:-)