Bill Castellon began working with plants after high school in green houses of rural Pennsylvania. In the mid-1970s he moved to San Francisco and was employed by a landscape contractor who maintained interior and exterior plants and landscapes. In 1980 Bill started his own maintenance business. At Merritt College, Bill studied Aesthetic Pruning and Bonsai with Dennis Makishima. Through the East Bay Bonsai Society, Bill met master Japanese garden builder Mas Imazumi. For over eight years Mas mentored Bill, teaching him the art and mechanics of traditional Japanese rock placement and garden building. In the mid-1990s Bill shifted from maintenance to designing and building gardens with a Japanese aesthetic.
In 2000, Bill and collaborator, Dick Austin, won two gold medals and one silver medal for their design at the San Francisco Garden Show. In 2001, Bill interned with head gardener Tokushirou Tamane at Kinkauji (the Golden Pavilion) in Kyoto, Japan. Bill is president of the Friends for the Japanese Garden at Lake Merritt, Oakland, and regularly volunteers at the Merritt Pruning Club, teaching classes and leading groups at the Japanese Garden at Lake Merritt and at Hakone Gardens. Customers and students seek out Bill for his expertise in pruning Black Pines, Maples, other plants suitable for traditional Japanese gardens, as well as a wide variety of common shrubs and trees.
Bill and his crew of skilled craftsmen specialize in gardens with a Japanese aesthetic. Ricardo, Arvidio and Roderico Carrillo are experts at working with stone, and are highly experienced in moving and placing boulders. By using traditional Japanese methods, Bill and his crew are able to place large boulders into challenging spots with precision. Bill considers rock placement an art form.