Born in Santa Monica, California, Evans was the youngest son of horticulturist Hugh Evans, who specialized in exotic plants. Bill Evans joined the U.S. Merchant Marine in 1928. He then studied geology at Stanford University, leaving a year before graduation to help his father and older brother, Jack, develop a commercial nursery. The Evanses partnered with Jack Reeves in the 1930s to establish Evans and Reeves Nursery in Brentwood, California. The clientele included Greta Garbo, Clark Gable, Elizabeth Taylor, Walt Disney, and other Hollywood celebrities. Disney hired the Evans brothers to create a landscape for his home, which led to their work on Disneyland, in Anaheim, California.
For Disneyland, Evans worked with landscape architects Ruth Shellhorn and Joseph Linesch on the original design of the park, creating fictive landscapes to emulate the places featured in the park, from the Mississippi River to African jungles. In the 1960s Evans was hired as director of landscape design to help develop the master plan for Walt Disney World in Florida, opened in 1971. Retiring from Disney in 1975, he continued to consult on new elements for Walt Disney World, including Disney’s Animal Kingdom, Disney-MGM Studios, Typhoon Lagoon, Magic Kingdom, and Discovery Island. With his former collaborator Joseph Linesch, he created the landscape design for EPCOT Center (1982). Evans also consulted on Tokyo Disneyland (1983), Disneyland Paris (1992), and Disney’s California Adventure (2001). He contributed to the conceptual landscape design for Hong Kong Disneyland (2005), which opened after his death. Evans wrote for many periodicals, including Pacific Horticulture and Sunset Magazine, and published the book Disneyland: World of Flowers (1965). In 1982 he was named a Fellow of the American Society of Landscape Architects. He continued to consult on landscape design until just weeks before his death at the age of 92.