Purpose: Greener on the Outside for Prisons (GOOP) is a therapeutic horticulture programme targeting the high levels of complex health and social care needs in prisons in England. The COVID-19 pandemic and resulting lockdowns led to unprecedented disruption in prisons in England. This paper examines the experiences of prisoners both during and post-lockdowns in four prisons, to understand the effects of participation in GOOP on health and wellbeing after the disruption of restrictions, and identify implications for developing this programme further. Design/methodology/approach: The paper is based on original qualitative data gathered from in-depth narrative-based interviews and focus groups with prisoners and staff in four English prisons. Audio data was transcribed and subject to a thematic analysis, drawing from a realist-informed lens. Findings: Thematic analysis revealed five key themes: reimagining the GOOP context; increasing empathy between participants; building sense of coherence; reconnecting with nature and a joined-up connection with provider services. The main arguments centre on horticulture in prisons remaining under-utilised as a means of promoting good health and wellbeing, although there is enthusiasm from staff to provide green spaces for the most vulnerable prisoners and develop a range of mechanisms to connect people in prison with nature. Originality/value: This paper focuses on new knowledge arising from an unprecedented situation in English prisons, from key stakeholders on the frontline of garden activities. Accounts demonstrate the extent of the health and wellbeing benefits of participation in such activities in this challenging environment, which has implications for practice for prisons more widely.