Landscape architecture is embarking on a new design frontier, one where its practitioners are increasingly being asked by clients to design using credible evidence and to ensure design performance Ð to become a profession of evidence-based landscape architecture. Current literature explains the benefits of practicing evidence-based design (EBD) including: ensuring design performance, justifying client investment, quantifying the value of design, systematically managing complex projects, marketing the firm to clients, attracting the most innovative designers to the firm, and adding to the knowledge base of the landscape architecture field. However, little is known about how landscape architecture firms are engaging evidence-based design in daily practice. This thesis examines how four leading landscape architecture firms (Design Workshop, Mithun, Sasaki Associates, and OLIN) have developed unique EBD approaches to integrate, apply, and propagate evidence-based design in professional practice.