Any grammar engineer can tell a good grammar from a bad one, but there is no commonly accepted taxonomy of indicators of required grammar refactorings. One of the consequences of this lack of general smell taxonomy is the scarcity of tools to assess and improve the quality of grammars. By combining two lines of research — on smell detection and on grammar transformation — we have assembled a taxonomy of smells in grammars. As a pilot case, the detectors for identified smells were implemented for grammars in a broad sense and applied to the 641 grammars of the Grammar Zoo.