Laurenz Greene, 100, a retired head of the horticultural department of Purdue University who became a consultant to the Agriculture Department and the Agency for International Development, died of cardiac arrest Dec. 8 at the Manor Care nursing home in Arlington.

Dr. Greene, a resident of Arlington since 1951, was born in Kansas. He graduated from Iowa State College and earned a doctorate at the University of California in 1932. He joined the Purdue faculty in 1917 and remained there until his retirement in 1950.

In 1947, he became a consultant to Agriculture's Office of Foreign Agricultural Relations. He supervised research in production of coffee and other crops in El Salvador and Ecuador. Later, he worked for Agriculture and AID in Washington.

Dr. Greene was a former president of the American Society of Horticultural Science. He was a member of the American Association for the Advancement of Science, the American Society of Plant Physiologists, the American Society of Agronomy and Soil Science and other professional organizations.

His first wife, the former Gertrude Mereness, died in 1941.

Survivors include his wife, the former Jennie Volk Watkins, of Arlington; two adopted daughters, Brenda Watkins Greene Fox of Nokesville, Va., and Sharon Watkins of Alexandria, and two grandchildren.