What happens when you put a therapeutic tree nursery inside a high-security prison? This talk covers the practicalities and surprises of setting up and running horticultural programmes in custodial settings, from negotiating with security to working alongside people with complex and often severe mental health conditions. We'll look at why plants and growing things seem to reach people that other interventions don't, what the evidence says about horticulture and behaviour change in the criminal justice system, and what it's actually like to spend your days doing something that feels faintly absurd and occasionally profound. No horticultural or clinical background required.