Landscape architect Theodore Osmundson, regarded as the nation's leading expert on rooftop gardens, has died after a brief illness. He was 88.

Mr. Osmundson, a Kensington resident, practiced in San Francisco since 1946 and founded the firm of Theodore Osmundson & Associates. He wrote "Roof Gardens: History, Design and Construction" (1999, W.W. Norton & Co.), widely considered the bible of rooftop gardening.

His firm was hired to create the Kaiser Center roof gardens at the urging of Edgar Kaiser Sr., who had worked in New York City in an office that overlooked the Rockefeller Center's rooftop gardens. When it opened in 1960, the Kaiser Center in Oakland had the largest roof garden in the world, with water, Japanese maples, olive trees and grass covering 3 acres atop three buildings.

Mr. Osmundson also designed city parks, private gardens, beaches and wilderness trails throughout the state. He contributed to the study of land use for Sequoia-Kings Canyon National Park, designed college campuses and designed levees in Idaho.

He also enjoyed photography and traveled extensively across the globe with his wife, Lorraine, an architect and real estate agent. They sought out rooftop gardens for inspiration, especially in Europe, where such gardens are more popular and sometimes are required by law to soak up excess rainfall and absorb pollution.

Mr. Osmundson was born in Virginia. He came to California in 1943 by way of Iowa State University, where he earned a degree in landscape architecture. He worked briefly for Thomas Church and Garrett Eckbo, both considered pioneers of California landscape architecture, before founding his own firm with Iowa State classmates John Staley and Jack Gibson.

At the time, the profession was moving away from the formal garden sensibility popular on the East Coast and moving toward less formal, more natural gardens that fit the casual California lifestyle.

He is also credited with improving the professional stature of the American Society of Landscape Architects by successfully pressing for the first state licensing law for landscape architects in the United States. He served as the society's Northern California chapter president in the 1950s, and was the society's national president from 1967 to 1969, earning numerous awards from the group. He served as president of the International Federation of Landscape Architects in 1991 and 1992.