There are a lot of questions asked about cordylines, probably as they have suffered from the bad winter we had. I don't know much about this plant but if you look at the gardening questions page, to the right under "by popular genus", you may get your answer here. Good luck...:o)

Yes - you can cut them down by half, or back down to the ground - this might mean they shoot from the base, or they may never recover from the winter.