The best time to put up a Christmas tree is in late November or early December. However, the exact timing can vary depending on personal preference and cultural traditions. Some families may choose to put up their tree earlier or later, depending on their schedules or holiday plans. It's also important to consider the type of tree you want to get and how long it will take to decorate it. If you're planning on getting a live tree, you'll want to make sure you have enough time to take care of it and keep it alive until Christmas.