of butterfly iris. It is the yellow version and the clump is about 3 feet wide. The rhizomes are so tightly packed together that a shovel is not adequate for the job. We need to reduce the size of the clump. Thanks.
I use a potato fork sometimes to get huge clumps broken apart into manageable pieces. I've also been known to use an old (rusted up) pruning say to saw through root masses.
I have a funky cheap sturdy steak knife, the kind they give you at rib restaurants. It saws through all kinds of roots nicely and because the blade is relatively short, I don't miss & cut things I don't want to cut.
You get them at restaurant supply places. I disinfect mine in between uses -- I don't want to spread plant viruses. More of an issue with hostas.
Pitchfork ... heave it out of the ground and hose the dirt off the roots. Then start cutting off good-looking rhizomes with ofionnachata's steak knife. I used to use a drywall saw.
i agree with lazygardens, i've had to do several large divisions (read favors for other people because i hate seeing plants suffer) last year and that's what i did, dig them up, hose 'em off and get in there with a blade. Serrated blades are better, i used a flat one once and the work was harder than it had to be.