Abstract Tree planting is increasingly being adopted as a strategy to address global change, including mitigation, adaptation, and restoration. Although reforestation has long been central to forest management, the desired outcomes of traditional and emerging tree-planting strategies face barriers linked to a lack of ecological diversity in forest nurseries. In the present article, we outline how insufficient diversity in nursery seedlings among species, genotypes, and stock types has impeded and will continue to hinder the implementation of diverse ecological or climate-suitable planting targets, now and into the future. To support this, we demonstrate disparities in seedling diversity among nursery inventories, focusing on the northern United States. To overcome these challenges, we recommend avenues for improving policy and financing, informational resources and training, and research and monitoring. Absent these advances, current seedling production and practices will fall short of ambitious tree-planting goals proposed for forest restoration and global change mitigation and adaptation.