The information below is from the City of St. Charles. https://www.stcharlescitymo.gov/575/Christmas-Tree-Recycling
The City usually offers free recycling of live Christmas trees the first two weeks of January on your regularly scheduled yard waste day of the week. In order for your tree to be accepted for recycling, it must be free of any lights, decorations, or bags. Also, any trees over six feet in height should be cut in half prior to being placed at the curbside.
For questions, contact your local Republic Services customer service representative at 636-255-6142 (Monday through Friday) or 636-947-5959 (Saturday).