The perceived benefits of outdoor learning have influenced recommendations and policies alike in early childhood education, yet one component (garden education) in Head Start preschools is inconsistent and researchers do not yet know why. The purposes of this qualitative interview study were to explore preschool teachers' experiences and perceptions of incorporating garden education into a preschool curriculum for children from low-income families and to develop a grounded theory-based conceptual model to explain the findings. Causal conditions included being comfortable in nature, having administrative support, focusing on safety, and reacting to weather. The intervening conditions were teacher knowledge and skills, program structure, resources and physical supplies, and human resources. The strategies for implementing sustainable use of preschool gardens were employing child-directed practices, applying multi-curricular techniques, incorporating health education, and engaging the community. The consequences identified for using preschool gardens were impacting whole child learning, influencing health, and exposing children to nature. Holistic integration of the results into the current literature suggested several opportunities for pre-service teacher education, professional development, and assessment tool development and validation.