I know a lot of people cut their Xenia, but I have a slightly different method.
I move a piece of
live rock next to a stalk or stalks and direct the current so it directs the Xenia toward the rock. In 2-3 days the stalks will eventually attach themselves to the rock and you can move the rock out of your tank. I had to do this with some Xenia that was touching my Candy Coral.