Abstract   I conduct an ethnography of the public policy processes around urban environmental governance in Boston, MA, Philadelphia, PA, and Baltimore, MD. In particular, I examine the structure and functioning of the public policy networks of the urban tree initiatives in order to investigate the expanding role of NGOs in public service delivery, especially related to sustainability and climate adaptation. This study concludes that urban partnerships often lack network structures that exhibit the centralization and hierarchy to roll out public programs smoothly. An overly horizontal structure leads to overlaps and gaps in management functions. Inadequate hierarchical control by public agencies increases the likelihood of gridlocks in service delivery. From an urban governance perspective, the prominent role of NGOs increases accountability of the public programs in certain limited capacities, while it creates systemic risks that compromise their legitimacy in ways that merit further investigation.