That's a tricky one! Cats love the scent and glitter of Christmas trees, so it's hard to keep them away. One way to discourage cats from climbing the tree is to hang strings of bells or tinsel from the branches. The sound of the bells will startle them and keep them away. Another method is to place a few cat toys or a scratching post near the tree, which might distract them from the tree. Finally, you could try spraying the tree with a citrus-scented spray, as cats don't like the smell of citrus.