That's a great question! Cats can be quite the curious creatures, and they often see a Christmas tree as an inviting plaything. There are a few things you can do to deter them from climbing it. First, you can try placing aluminum foil or sticky tape around the base of the tree, as cats generally dislike the feel of these materials. Additionally, you can try using scents such as citrus or pepper spray, as cats often find these unpleasant. Finally, you can also create a physical barrier, such as placing the tree in a room that the cat is not allowed to enter or using a baby gate. Good luck!