mother nature doesn't cut them off :o)

By cutting them down by half they are less susceptible to wind rock. But I don't bother unless I am lifting and splitting them I leave mine alone.

Once leaves go brown & crispy, you can cut them off. Rotting leaves can harbor pathogens & eggs for the dreaded iris borer.

ty,i would love more but ive no space,so i can split them then

Yes simple to do but remember don’t deep plant them.