Hi S,
It looks like verbena hastata, but the flowers look shorter than normal. That might be because it is a new smaller plant. It is a native wild flower that attracts butterflies. It grows quite tall though. So if it is in the wrong spot, you can move it in the spring to a better location. Also, it can re-seed, but the seedlings are easy to remove if unwanted.
Remy

Thanks Remy! You re absolutely right...I googled some pics of this and this is exactly what it looks like...

Here we call it blue vervain.

I ll let it stay...

Thanks again!

it looks more like an Agastche to me, also called a giant Hyssop. here are two in my garden, they are 'desirable' weeds. I have a few volunteers but I planted these.

PL

Here is a link that might be useful: {{gwi:1351011}}