Caring local biodiversity in a healing garden: therapeutic benefits in young subjects with autism

•Autism spectrum disorder (ASD) subjects were constituted as “Biodiversity Custodians”.•ASD subjects were involved in the care of landraces within an enabling garden.•Plant functional traits were determined for evaluation of landraces germplasm.•ASD subjects improved their independence, adaptive behaviour and interaction skills.•Caring of landraces promoted the role of ecosystem services in human well-being.