To explore the health benefits of nature-inspired indoor interventions, three experimental studies conducted at the Department of Horticulture and Landscape Architecture, NTU, examined the combined effects of horticultural therapy and aromatic inhalation on human psychophysiological well-being. These studies were undertaken in response to the growing demand for indoor nature-based interventions, especially during the COVID-19 pandemic, when access to outdoor environments was restricted. Participants were divided into three groups, each engaging in a distinct activity—leaf printing, kokedama (moss ball making), or painting still lifes with vegetables. During the sessions, lavender (Lavandula angustifolia) and Douglas fir (Pseudotsuga menziesii) essential oils were diffused to create a forest-like atmosphere, mimicking the relaxing effects of forest bathing.
Physiological measurements via biosensors (Fig. 4) indicated relaxation responses across all activities, including reductions in heart rate, low-frequency HRV, and beta/gamma brainwaves as well as increases in the standard deviation of normal-to-normal intervals, high-frequency HRV, and alpha waves. Subjective assessments using the State-Trait Anxiety Inventory showed significantly lower anxiety levels following the activities.
These findings suggest that combining multisensory horticultural engagement with olfactory stimulation can effectively regulate autonomic nervous system activity and promote emotional balance. The integration of hands-on creative tasks with plant-derived aromatic elements provides a meaningful and practical approach to enhancing mental and physiological health in indoor settings. This strategy is particularly relevant in urbanized societies or during health crises that limit exposure to natural outdoor environments, highlighting its potential as a restorative practice to support well-being.
Figures 4. Leaf printing activity at NTU's Horticultural Therapy Lab 1.
(Participants engage in leaf printing during a nature-inspired therapeutic session while wearing biosensors to measure physiological responses.)
Figures 5. Leaf printing activity at NTU's Horticultural Therapy Lab 2.
(Participants engage in leaf printing during a nature-inspired therapeutic session while wearing biosensors to measure physiological responses.)
Figure 6. Image of moss balls (kokedama technique) created as part of a horticultural therapy session.
(The participants wore biosensors to monitor physiological changes during the activity.)