Although there is growing interest among health and social care professionals in the social and therapeutic value of horticulture, there is little evidence that demonstrates the range of outcomes for vulnerable groups, including those with learning difficulties and mental health problems. This report addresses this gap in knowledge and presents the findings of the Growing Together project, the first detailed study of horticulture and gardening projects across the UK. The report is aimed at policy makers, professionals, researchers and students in the fields of health and social care and occupational and horticultural therapy who are hungry for hard evidence in this new field, as well as anyone interested in addressing the needs of vulnerable and socially excluded adults. The Growing Together project is a partnership between Loughborough University and Thrive and has been funded by the Big Lottery Fund. This report complements a practice guide, Growing together: A practice guide to promoting social inclusion through gardening and horticulture, which is also available from The Policy Press.