Surgical patients have to deal with multiple stresses during hospitalization such as pain and physical discomfort, fear of medical procedures, and unfamiliarity with hospital equipment and environment. Using a blood cortisol test, one of the well-known measurements of stress responses, this study performed a randomized clinical trial with surgical patients to evaluate if plants in hospital rooms have therapeutic influences. Fifty-two patients recovering from a surgery were randomly assigned to hospital rooms with or without plants. Patients in the plant treatment room viewed seven species of foliage and flowering plants during postoperative recovery periods. Level of blood cortisol were compared between plant room patients and control room patients before surgery and discharge for two months. Patients in hospital rooms with plants and flowers had a significantly lower level of cortisol (p<0.044) as compared to patients in the control rooms. Male patients in plant rooms also showed a significantly lower level of cortisol (p<0.04) as compared to those in control rooms. No significant differences, however, were noted in female patients between control and plant rooms. The results of this study suggested that experience of plant interactions may positively affect patients' stress responses, thus increase relaxation. Further research will support hospital administrator and medical doctor decisions to use plants as a healing modality.