Russell J. Seibert Renowned Botanist Russell J. Seibert, 90, a botanist who was the first director of the Los Angeles County Arboretum & Botanic Garden as well as Longwood Gardens in Kennett Square, Pa., died Nov. 28 at a nursing home in Sarasota, Fla., of complications from Alzheimer's disease. Dr. Seibert was director of the Los Angeles site from 1950 to 1955 and then of Longwood Gardens until 1979. At Longwood, he oversaw the transition from a private estate belonging to Pierre S. du Pont to a horticultural display garden. After retiring, he moved to Sarasota, where he served as curator emeritus of tropical horticulture at Marie Selby Botanical Gardens. Russell Jacob Seibert was raised on a farm in Illinois. He was a graduate of Washington University in St. Louis, where he received master's and doctoral degrees in botany. He worked for the Agriculture Department in the 1940s, organizing the construction of a rubber plantation in Haiti as well as conducting plant explorations in the jungles of Central and South America. He was former chairman of the Williamsburg Garden Symposium and president of the American Horticultural Society. Survivors include his wife of 61 years, Isabelle "Deni" Pring of Sarasota; three children; and six grandchildren.