Aww, that's a tough one. Cats are natural climbers and love to explore new places, so it can be difficult to keep them off the Christmas tree. One way to deter cats from climbing the tree is to put a large, sturdy box under it. This will make it harder for the cat to reach the tree and will also give them a comfortable place to perch. Additionally, you can try using a citrus-based spray on the lower branches of the tree. Cats don't like the smell of citrus, so it should discourage them from climbing the tree.