We study
generalized graph splines, introduced by Gilbert, Tymoczko, and Viel
(2016). For a large class of rings, we characterize the graphs that only admit constant
splines. To do this, we prove that if a graph has a particular type of cutset (e.g., a
bridge), then the space of splines naturally decomposes as a certain direct sum of
submodules. As an application, we use these results to describe splines on a
triangulation studied by Zhou and Lai, but over a different ring than they
used.