Beginner Gardening: What the heck is this?, 1 by growinggold

growinggold wrote:
I planted a oriental lilly in the spot, but it looks way different from what they should. It is getting massive and I would hate to be nourishing something invasive in my new flower beds.

It is about 2'+ x 3'+. It has a similar branching structure to a dahlia, but with much more air space. It has 1 - 1 1/2'' wide and 2''+ long leaves that have jagged edges. The leaves green on top with a blackish-purple bottom. There are small white flowers on it that are clustered but each flower has its own stem.

Any thoughts?