Well, that's a tricky one. Cats are naturally curious and playful, so it's hard to keep them away from something as shiny and tempting as a Christmas tree. You could try using aluminum foil or tin foil on the lower branches of the tree to create a texture that cats don't like. Or you could try placing citrus fruit or other scents that cats dislike around the base of the tree. Finally, you could try distracting the cat with other toys or activities to keep them away from the tree.