He held the office of First Lord of Trade and Foreign Plantations between 30 May 1702 and April 1707. In this role, Weymouth is reputed to have introduced the Lord Weymouth Pine ("Pinus strobus"), in 1705. He planted it extensively on the estate at Longleat. The Lord Weymouth Pine was useful for ship masts, in that it grew tall and slender. Weymouth's reputation in connection to the pine is doubtful, since the name really derived from the explorer George Weymouth, totally unrelated, who first discovered this pine growing in colonial Maine. All Thomas Thynne did was to arrange for its importation, and prefix a "Lord" in front of the Weymouth in the tree's official appellation.