Mature urban trees dwelling on old masonry walls are a rare urban ecological and landscape treasure. These ‘stonewall’ trees denoting synergy between nature (trees) and culture (masonry) are worth preserving. This study aims to identify factors influencing public attitude toward this important but threatened natural-cum-cultural asset in a compact city milieu. Evidence is solicited from a face-to-face questionnaire survey involving 800 citizens of Hong Kong. Results indicate that Hong Kong people generally appreciate the existence of stonewall trees. Younger adults harbored doubts about their value, whereas the older ones were more sympathetic. Local residents of the suburbs that host the majority of stonewall trees registered stronger commitment than non-local residents. Community attachment had positive effects across both resident groups, but length of tenure was not a key factor. This suggests that affinity for stonewall trees is a function of the affective bonding between people and the community where they live. Deep engagement with the local community elevated the desire for preserving the walls and associated trees. The findings are important for understanding public perception and enlisting support from the larger society for preserving the urban asset against mounting pressures for urban development and renewal.