Abstract: The beneficial effect of nature on patients with mental disorders is of particular importance. There has been an increase in mental illnesses in recent years, but research on the design of healing gardens for mental and behavioural disorders remains limited. This paper is part of a wider study that aims to investigate the effect of selected design elements of healing gardens on patients with mental disorders. This study examines the effect of seasonal colour change in plantings in the design of healing gardens on patients suffering from psychotic disorders by using a questionnaire survey and by recording and analysing human behaviour. Images depicting seasonal colour change in different plantings were viewed on a computer monitor by patients. Patients’ behaviour was studied using biosensors for eye-tracking, facial expression analysis and galvanic skin response. The results showed that differences in gender and age between participants did not affect their preferences. However, it appeared to be more difficult to positively affect the emotions of male participants compared to female participants. Seasonal colour change in a tree canopy created positive and intense emotions in the patients. Based on the results, the use of deciduous trees is proposed in the design of healing gardens for patients with psychotic disorders to create seasonal colour change. Further research is necessary to obtain more detailed design recommendations for landscape architects.