Larry Mitich, a weed scientist emeritus for the University of California, Davis, Cooperative Extension, was a recognized authority on weeds that plague farmers' crops. But within the botanical world, Mitich was known for his passion for cacti and succulents and the people who cultivated and studied them. He died Wednesday in his Robbins Hall office, where he continued to work nearly every weekday since his retirement five years ago. Mitich, who had a history of heart disease, was 73. "I think his heart just wore out," said his wife of 45 years, Charlotte. Mitich was president of the Cactus and Succulent Society of America for the past 4 1/2 years. He wrote numerous articles for the society's scholarly Cactus and Succulent Journal. He was also past president of the Weed Science Society of America and Western Society of Weed Science and past editor of Weeds Today magazine and the North Central Weed Science Society's Research Report and Proceedings. During his 34 years in academics, he wrote 387 articles, papers and bulletins. He was named a fellow of the North Central Weed Science Society, Weed Science Society of America and the Western Society of Weed Science. In 1985, the Western Society of Weed Science named him Outstanding Weed Scientist. For nearly 30 years, his wife said, Mitich wrote a column "Intriguing World of Weeds" for the Weed Society of America quarterly journal Weed Technology. His topics ranged from Bermuda grass and dandelions to tansy ragwort and velvetleaf. On Wednesday morning, Mitich attended a meeting of the Davis Botanical Society, an outreach and support group for the UC Davis Herbarium. He had been treasurer of the group since it was created in 1991, said Grady Webster, professor emeritus of plant biology. Mitich returned to his office after the meeting. A vegetable crops department administrative assistant, asked by Mitich's wife to check on him, found him dead at his desk shortly before 5 p.m. Mary Williams, Yolo County supervising deputy coroner, said no autopsy was scheduled because Mitich had been under the care of a physician for his heart condition and appeared to have died of natural causes. Born in Lead, S.D., Mitich grew up in eastern Wyoming where, he later wrote, he developed his love of cacti and succulents. Prickly pear, morning star cactus and other cactus grew on his parent's ranch and in the hills surrounding his hometown of Newcastle. With water too scarce for a flower garden, his mother filled the windows of their home with houseplants. When he was in third-grade, his mother bought two varieties of snake plant for a dime each. "That was the start of my interest in succulents," he wrote in the cactus society March/April 1996 newsletter. His personal collection of books and other publications on cacti and succulents is one of the largest of its kind in the nation, his wife said. His interest in succulents took him to Africa for plant safaris twice, once to Rhodesia and two years to South Africa, she said. Mitich earned all three of his degrees -- a bachelor's in animal science and master's and doctorate in agronomy from the University of Wyoming. He started his doctoral studies at Cornell University, but left to spend a year working on the family ranch after his father had a heart attack. In between his first two degrees, he served in the Army in Germany for two years during the Korean War. After getting his master's, he spent 4 1/2 years teaching at Afghanistan's University of Kabul as part of the U.S Aid for International Development program. Mitich joined UC Davis Cooperative Extension in October 1980 after more than 17 years as an agronomy professor with the North Dakota State University Cooperative Extension Service. He retired from UC Davis in May 1995. Active in the cactus society for a number of years, Mitich became president in January 1996. Soon after, he began writing biographical sketches of famous cactus and succulent botanists and horticulturists. Webster said Mitich was well-known among botanical circles for those articles, which were published in the society's newsletter. Ellen Dean, director and curator of the UC Davis Herbarium, said Mitich was a "very quiet, kind man" who would spend hours researching plant pioneers. "He would try to bring a plant alive for people, so he would try to find out who discovered it and where and how it was discovered," Dean said. In addition to his wife, survivors include five brothers and one sister, all of Wyoming, and numerous nieces and nephews. One nephew, Jim Murray, is a UC Davis veterinary and animal science professor. A graveside funeral next Tuesday will be private. Arrangements were by Davis Funeral Chapel. Memorial donations were suggested to the UC Davis Herbarium or to the Cactus and Succulent Society Research Fund. Checks for the herbarium should be made to the UC Regents and sent to: Ellen Dean, Department of Plant Biology, UC Davis, One Shields Ave., Davis, CA 95616. Cactus society donations should be mailed c/o Mindy Fusaro, P.O. Box 2615, Pahrump, NV 89041-2615.