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<i>Phytophthora </i>is a genus of destructive plant pathogens. Certain species are damaging to native ecosystems, forestry, and the horticultural sector, and there is evidence of their dissemination in plant imports. Horticultural nurseries are central nodes of the plant trade and previous studies have found a high diversity of <i>Phytophthora</i> associated with plant nursery stock. It was subsequently hypothesized that green waste disposal sites in nurseries could harbour diverse <i>Phytophthora</i> communities and act as a pathogen reservoir and conduit, facilitating further <i>Phytophthora</i> infection of nursery stock and its spread into the wider environment. This project identified <i>Phytophthora </i>species associated with green waste at three Scottish nurseries by sampling material from waste piles, water run-off from piles, and roots from discarded plants. Species were identified using a baiting method and sequencing of environmental DNA. Plant nursery green waste was shown to harbour diverse and varied <i>Phytophthora</i> species assemblages, with differences among nurseries reflecting biosecurity management practices. Eighteen <i>Phytophthora </i>species were detected in the samples, including the highly destructive pathogens <i>P. ramorum</i> and <i>P. austrocedri</i>. Results suggest that the improved management of waste, for example through effective on-site composting, is essential to reduce the risk of<i> Phytophthora</i> pathogens spreading from nurseries into the wider environment.