Costco usually starts selling their Christmas trees in mid-to-late October. The exact date can vary depending on the region, so it's best to check with your local Costco or their website for more information. It's important to note that the Christmas tree selection at Costco is often limited, so it's a good idea to buy one early to ensure you get the type of tree you want. Costco typically offers a range of sizes, styles, and types of trees, including pre-lit options, so you can find the perfect one for your home.