D/B, you are very welcome. I hope you don't misunderstand, but are you absolutely certain your plants are Cordylines and not Yucca? The reason I ask is Cordyline plants are not usually sold much in the US and rarely as far north as you are. I see you are in zone 5. You may have noticed when you searched for a site to show me what they were, it was a site from the UK. Most of the UK is zones 8 and a bit of zone 9. There is one very small area that is zone 7. Some Yucca can be hardy to zone 5. Here's what some Yuccas look like.
If you do have Cordyline you will need to wrap the leaves together somehow. I would suggest something soft and with a bit of give like pantyhose. Cut off the foot and then cut the leg sections in rings. Then cut the ring so you have a length you can use to tie with. Then you will need to cover the plants and insulate them. You don't want moisture to get to the crown of the plants so you will have to keep the snow off whatever you wrap them with. Then you can put piles of leaves around them and secure the leaves with some type of netting such as bird netting. Here's some ideas.
From this site:
3. If any of you are growing tropical plants in your garden like bananas, these will need protecting as well. If they are growing in pots they can be moved inside for the winter, but if they are too large, or planted in the ground they will need some winter protection. The easiest way to protect bananas is to cut back any large low growing leaves to the trunk. Then put a circle of wire mesh around the stem and fill this with straw. Then wrap the whole plant with hessian sack or fleece.
Finally put a cap of polythene on top (but do not cover totally) to stop some of the winter wet running down into the plant, hopefully this will protect your plants from the worst of the winter weather. The same method of protection can be used for large cordyline's growing in the ground, or tree ferns. This should keep the plants safe until you unwrap them again next spring.
From this site:
Protect the crowns of tree ferns and insulate their trunks by wrapping them in layers of fleece or hessian stuffed with straw. Cordylines and palms should be treated similarly, by tying their leaves into bunches, to protect their crowns.