The emerging profession of arboriculture has influenced Australian urban landscapes over the past decade. Arborists manage the urban forest as a core component of urban sustainability. We analyse qualitative interviews with 53 professionals involved in tree management in six eastern Australian cities to determine the ways in which a concern with risk management has shaped both the urban forest and the professional status and role of arborists. We found tree‐related risk has, in part, worked against urban greening by reducing tree size. However, an emerging risk culture has encouraged the development of the profession of arboriculture, which, in turn, has pioneered sophisticated ways, familiar to neither engineers nor ecologists, of ensuring the cohabitation of people and trees.