Various embodiments related to a tree guard. One embodiment provides a modular tree guard assembly. Various other embodiments disclosed include one or more of the following: a multi-purpose top rail unit facilitating flexible installation of various side panel units and top rail accessories; modular side panel units including decorative units and urine guard units; corner and other post units; and various adjustable foot units. In one embodiment, a sign holder unit of the tree guard assembly is provided with different tamper proof bolts than are other elements of the assembly such that control over signage on the tree guard may be effectively given to a different entity than an entity with control over assembly of the rest of the tree guard unit. Various other embodiments related to tree guards are disclosed.