Thaddeus C. Green, 96, a retired senior groundskeeper for the National Institutes of Health in Bethesda, died of uremic poisoning Monday at Suburban Hospital in Bethesda.

Mr. Green was born on a farm in Stafford County, Va. When he was a child, his family moved to a farm in the Pooks Hill section of Bethesda and Mr. Green grew up there and became a farmer.

In 1920 he went to work on the estate of the late Dr. David Fairchild in Chevy Chase and learned gardening. He remained with the Fairchild family until 1929, when he went to work for the Luke I. Wilson family on the site of what is now NIH. When NIH was built on that land, Mr. Green became a groundskeeper for the government and worked there until his retirement in 1951.

Mr. Green also had a second job.From 1940 until his retirment in 1961, he worked nights as a ticket taker at the old Hiser movie theater at Wisconsin Avenue and Montgomery Lane in Bethesda. The theater site is now a Metro station.

Mr. Green was a member of St. John's Episcopal Church in Chevy Chase.

His wife, the former Lillian Keys, died in 1971. A son, Elmer R., died in 1975.

Survivors include two sons, Cecil B., of Alexandria, and Hobart C., of Bethesda; three daughters, Louise Lord of Garden Grove, Calif., June G. Abert of Bethesda and Barbara Bailey of Lexington, Ky.; 10 grandchildren, four great-grandchildren and one great-great-grandchild.