That's Aquilegia - Columbine Plants. They do flower once they reach mature size and need sun.

I love Aquilegia. It is very pretty and dies back in the summer. I have lots of different ones and I am still collecting them.

it may be a wild thalictrum, the point where the leaves come from the root doesn't look typically like an aqueliga.

if you really don't like it try spraying it with a weedkiller like round-up.

I also thought Thalictrum.

I still say Aquilegia. It's an exact match to the one in my garden.

I'd thought thalictrum too but looked it up to make sure and the leaves in the illustration had fine saw toothed margins. So checked my plant in the garden and it was sort of half way between the illustration in the book and the picture here. The root looks more like thalictrum than aquiligia, and Elaine implies that it sends out runners, which Aquilegia doesn't do and wild thalictrum does.

And this one is fresh bright green, not the slightly glaucous colout of the Aquilegia.

Flowering will settle the question as thalictrum will have sprays of tiny yellow flowers totally different from Aquilegia.

Looks like Thalictrum aquilegifolium to me too. I have both the creamy white flowers and the purple on mine and they grow quite tall, up to 5ft in my garden.