Rigorous abstract knowledge, such as academic knowledge, is vital to a profession’s resilience against other modern professional competition. In the field of landscape architecture, a growing number of concerns about a lack of rigorous knowledge have been observed, which may jeopardise the jurisdiction of its professional practice. A study was conducted that collected behaviours and attitudes from various members of the American Society of Landscape Architects (ASLA) regarding how they accessed, disseminated, and applied knowledge in practice. Their responses concerning the knowledge were analysed by dividing and ranking the options according to the degree of knowledge abstraction. Knowledge abstraction refers to theories and commonplace best practices that are established within a profession through shared knowledge, experience, and research. The results showed that (1) most practitioners tended to access new knowledge through tacit experience, which is indicative of a lower level of abstraction in their practice; (2) design decisions were based less on higher and rigorously abstracted knowledge such as research findings and, in circumstances where it was deployed in the design process, such knowledge was seldom used to guide design independently; (3) the majority of practitioners rarely share knowledge through high-abstracted publications; and (4) compared with accessing relatively diverse levels of knowledge abstraction, practitioners were less resourceful in knowledge application and even less in dissemination. The knowledge acquired, used and circulated in the workplace of landscape architects—as indicated by this survey—is still not comprehensively abstracted to a rigorous level, which may provide an insight into the concerns of practitioners regarding this profession’s breadth of knowledge and jurisdiction.