HoosierHarvester said:Now that's not funny!!! 
It's about a 35'-40' length of concrete blocks. ...
Wow, I stand corrected.
This is a case for ... dynamite!
I take it the rhizomes go straight down below the level of the cinder blocks.
Could you use a "sharpshooter spade" (trenching spade with a flat blade) to cut down 12" below grade, all around the cinder block? Then uproot the iris' root ball at the same time you tip the cinder block on its side ... but still have to extract the root ball from the cinder block.
For the future, it might be worthwhile lining the cinderblock holes with heavy plastic film before filling with soil and plants. Then you could tug on the plastic like a sleeve.
BUT those rhizomes might have like all the air and drainage they got from being flush against a very porous surface.
