This paper examines how meaning making influences the content and currency of the evidence used to shape and support policy proposals. It does this by answering three linked questions: (1) How does context influence the forms of evidence employed in policy advocacy? (2) What practices are initiated by reference to the perceived need for evidence in policy formulation? (3) What effects do these practices have on the location of power within policy debates? These questions are answered and illustrated by examining how agents managed their relationship with the evidence they presented in promoting "green infrastructure" land use policy in Ireland.