Don't let your Christmas tree go to waste! Denver residents can recycle their Christmas trees from Dec. 31, 2012 through Jan. 11, 2013. The City & County of Denver's Treecycle program transforms discarded trees into much-needed mulch. To recycle your tree, remove all decorations and place by your recycling receptacle. Do not put trees in dumpsters or they will not be picked up by the city.