Anyone have any thoughts on how to get rid of this invasive species?

Unfortunately it's growing all through my iris rhizomes, so the key is, obviously, not killing my iris while trying to eradicate this jerk of a plant.

So far, I've just been pulling up the stalks, so at least it cant flower, seed or shade the things I want in the garden.

Clearly this is not doing much except stopping seeds.

Also, where I live, there are a lot of laws against herbicides and I'm also not interested in killing off any bee populations! I'd read about "Iron X" in another post and the user was having some success however I don't believe that the chemicals in that product are allowed where I am.

Any advice is appreciated, however I think I'm probably out of luck!

Kat