**Background:** School environments offer a promising setting for promoting children's health, and school gardening has gained popularity as an intervention to encourage healthier eating and physical activity. While prior reviews have reported benefits, quantitative evidence for changes in fruit and vegetable intake remains limited and often relies on self-report or non-randomized designs. This realist synthesis was designed to move beyond asking 'what works' to understanding 'how, why, and in what circumstances' school gardens improve health and well-being outcomes for school-aged children.
**Methods:** The authors used a three-stage systematic realist approach. Stage 1 involved searching Scopus, Web of Science, and PubMed for systematic and meta-analysis reviews published between 2012–2021 using the term 'school garden*'. Six reviews met inclusion criteria. Stage 2 screened the full text of these reviews to extract primary articles reporting positive health and well-being outcomes (defined as improved change determined quantitatively or qualitatively). Stage 3 reviewed the full text of each primary article to identify specific school gardening interventions. Data extraction followed the Template for Intervention Description and Replication (TIDieR) checklist. Analysis used Context–Mechanism–Outcome (CMO) configurations for each intervention, applying realist synthesis principles to identify underlying causal mechanisms.
**Key Results:** The screening identified 6 review articles, 65 primary articles with positive outcomes, and 35 articles associated with 24 distinct school gardening interventions. Interventions were conducted across Australia, the United Kingdom, the United States, India, Kenya, Bhutan, and Nepal, mostly in primary schools with children in Grades 2 through 6. Duration ranged from 6 weeks to 3 years. Key mechanisms included: (1) embedding nutrition-based and garden-based education in the curriculum; (2) experiential or 'hands-on' learning (growing, harvesting, preparing, and consuming produce); (3) family engagement and participation (volunteering, take-home activities, intergenerational learning); (4) authority figure engagement (teachers, principals, external experts as role models); (5) cultural context and tailoring for minority groups; (6) multi-pronged approaches (multi-level, multi-sectoral, multi-component strategies); and (7) reinforcement of activities for sustainability (repeated exposure, consistent messaging). Positive outcomes included increased fruit and vegetable consumption, increased dietary fiber and vitamins A and C intake, improved BMI percentile, BMI z-score, and waist-to-height ratio, improved children's well-being (social skills, confidence, sense of belonging), and improved family health behaviors.
**Clinical Implications:** This synthesis provides a theory-driven framework for designing and implementing school gardening programs. The findings suggest that no single mechanism operates in isolation; rather, a combination of curriculum integration, experiential learning, family involvement, cultural sensitivity, and sustained reinforcement works mutually to produce positive health outcomes. Schools and policymakers should consider these interacting mechanisms when developing interventions, particularly for addressing childhood obesity and food insecurity. The authors note that generalizability may be limited to high-income countries, as most programs were based in Australia, the UK, and the US, though some programs targeted low-income and minority populations within those settings.