Career
Born at "Mount Pleasant" near Loretto, Virginia, Garnett was schooled by private teachers as a child and later engaged in planting. He was not a candidate for reelection and instead returned to planting and later conducted a school for boys on his plantation. He wrote Lectures on Female Education: Comprising the First and Second Series of a Course Delivered to Mistress
Garnett"s Pupils, at Elm-wood, Essex County, Virginia (1824).
He was one of the founders of the Virginia State Agricultural Society, was vice president of the Virginia Colonization Society, and was a delegate to the Virginia Constitutional Convention of 1829–1830. Garnett died at his estate called "Elmwood" near Loretto, Virginia on April 23, 1843, and was interned in the family cemetery on the estate.