There are several scents that cats are known to dislike and can help keep them away from your Christmas tree. Some of the most effective ones are citrus, peppermint, eucalyptus, and lavender. Citrus is the most potent, but any of these scents can work as long as you place them strategically around your tree. You can also try using a citrus or peppermint spray on the tree itself to help deter cats from getting too close. Just remember to keep the scents away from your cat's food and water bowls to prevent any accidental ingestion.