The first thing to consider is the type of tree you want to bring into your home, per Daily Paws. Pine needles that fall from natural trees, if ingested, can cause serious problems with digestion for your cat, and the water that collects in the tree stand, filled with toxic fertilizer remnants, can be hazardous too, per Blue Cross. An artificial tree might be a safer option according to Treehugger, especially if you're unable to sweep off pine needles or closely monitor your cat's whereabouts. Or, you could choose a smaller natural tree that you can keep away on a table.
Spraying your tree with "cat deterrent" solutions is a good next step, per The Purring Journal. You can easily purchase one at the store or try homemade solutions. Cats are not the biggest fans of citrus smells. Cat expert Jackson Galaxy suggests keeping your feline friends away simply by filling a ziplock bag with lemon or orange rind, jabbing holes in the bag, and placing the bag under your tree. You can protect the base of the tree by pasting aluminum foil on the ground or using pine cones (or stones), reports The Purring Journal.
If you watch your cat closely enough, you know that he or she usually launches off surfaces to get to someplace higher, so moving away such furniture from around your Christmas tree might be best.