Sometimes a cat will want to climb up the Christmas tree because it is attracted by the decorations and ornaments. One way to deter the cat from the tree is to spray it with water or a citrus-scented spray. This will discourage the cat from approaching the tree and discourage them from climbing up it. You can also put a few thorny branches around the tree to make it uncomfortable for the cat to climb up. If you have a cat-proof fence, you can use that to keep the cat out of the tree area.