Effects of therapeutic horticulture on stress and anxiety in undergraduate vs. graduate students

College students worldwide experience persistently high levels of stress and anxiety, which negatively affect academic performance, well-being, and persistence. While therapeutic horticulture (TH) has demonstrated benefits for mental health, limited research has examined whether its effects differ between undergraduate and graduate students, who face distinct developmental and academic stressors. This study evaluated changes in perceived stress and anxiety following participation in a structured therapeutic horticulture program and compared outcomes by student status. Using a single-group pre–post design, data were collected across six academic terms between Fall 2021 and Spring 2024 from students participating in an eight-session therapeutic horticulture program at a large public university. Participants ( n = 222) completed the Perceived Stress Scale (PSS-10) and the State–Trait Anxiety Inventory short form (STAI-6) at baseline and after their eighth session. Paired-sample t -tests examined pre- to post-intervention changes, and independent-sample t -tests compared change scores between undergraduate and graduate students. Participants included 148 undergraduates (66.7%) and 74 graduate students (33.3%). Across the full sample, perceived stress, state anxiety, and trait anxiety all decreased significantly following participation (all p < 0.001), with medium to large effect sizes. Baseline comparisons revealed no differences between undergraduate and graduate students in stress or trait anxiety, though graduate students reported higher baseline state anxiety. Importantly, no statistically significant differences were observed between undergraduate and graduate students in the magnitude of change for any outcome measure, indicating comparable reductions in stress and anxiety across groups. Findings suggest that structured therapeutic horticulture programming is effective in reducing stress and both state and trait anxiety among college students, regardless of academic level. Despite differences in baseline stressors, undergraduate and graduate students demonstrated similar psychological benefits, indicating that therapeutic horticulture may operate through shared mechanisms such as nature engagement, skill mastery, and social connection. These results support the broader applicability of therapeutic horticulture as a campus-based mental health intervention and highlight its potential role in supporting diverse student populations.