thats quite normal as the old leaves drop of from the bottom and the new ones come from the top . the old leaves do offer some protection but you can cut them of if you want . i would soon when it gets much colder tie the leaves up so snow doesnt sit on them in light of all the lost cordylines last years harsh winter. take care bye for now .

Agree with Nosey, but pull off by hand anything that will come off. You can cut stubborn leaves off, but I'd leave those at this time of year and deal with them next Spring, when you can cut them off if necessary. You will need a very sharp pair of secateurs or scissors though, they're pretty tough to cut through.