A cover for Christmas trees which includes a tree-encapsulating bag or sheath provided with a center opening for receiving the trunk of the tree, a center string sleeve encircling the center opening and slidably containing a center perimeter string for tightening the center segment of the sheath against the trunk and an outside perimeter sleeve for containing an outside perimeter string, wherein the sheath can be extended entirely around the limits of the tree and the outside perimeter string tightened, to encapsulate the major portion of the tree inside the sheath. Multiple radial string sleeves slidably containing radial strings are also provided in the sheath, for shaping the sheath into a simulated landscape by forming pleats and scallops in the sheath. The cover can therefore be utilized as a decorative blanket which simulates a snow-covered landscape beneath the tree and as a dust cover for storing artificial Christmas trees or as a disposable or reuseable encapsulating bag for containing the needles of natural Christmas trees when disposing of such trees.