Hayes, Samuel (1743–95), politician, improving landlord, and amateur architect, was the eldest son of John Hayes of Hayesville, Co. Wicklow. He studied under a Mr Ford, before entering TCD on 8 January 1759. He registered at London's Middle Temple in 1761 (22 June), graduated BA from TCD in 1762, and entered Christ Church, Oxford, in the same year (16 November). Called to the Irish bar (1767), Hayes was sheriff (5 February 1773) and joint governor (1779–95) of Co. Wicklow. He was a colonel in the Wicklow Foresters and subsequently lieutenant-colonel in the Wicklow militia. His national career in politics began as a delegate for the county at the Volunteer convention of 1783. He was then elected MP for Wicklow borough (1783–90) and Maryborough (1790–95) and was politically linked to Sir John Parnell (qv), 2nd baronet, to whom he was related on his mother's side. Hayes was also governor of the Foundling Hospital and Workhouse (1786–95) and commissioner of stamps (18 July 1789–1795).
When he inherited the 4,500-acre Hayesville estate from his father he renamed it Avondale (the Avonmore river runs by it). He had built a house on the terrace above the river in the neo-classical style and is very likely to have been its architect. Establishing the Avondale forest in the late 1770s, he planted trees on a massive scale as both timber and ornament. Later, when an MP, he introduced a bill encouraging the cultivation and preservation of trees. Encouraged by ‘several respectable members of the Dublin Society’ (preface, p. vi), Hayes wrote A practical treatise on planting and the management of woods and coppices (1794). Intended to be a practical guide to the planting of trees and the managing of wood for timber, it was in fact Ireland's first full-length book on trees. It includes seventeen engravings executed by William Esdall (qv), but very likely drawn by Hayes himself. An amateur architect, he was partly responsible for drawing the plans for additions to the parliament building (1787–94). He also designed the market house in Monaghan, built for Gen. Robert Cunningham, afterwards 1st Baron Rossmore (d. 1801). A member of the Dublin Society from 1766, Hayes was later elected to membership of the RIA and was a member of its committee of antiquities in 1793.
Hayes married (2 October 1766) Alice Le Hunt, daughter of Thomas Le Hunt, MP and wide streets commissioner of Dublin, but died childless at Avondale (28 November 1795). The estate was initially inherited by Sir John Parnell. By the terms of Hayes's will, it eventually passed to his cousin William Parnell (qv), brother of Sir Henry Brooke Parnell (qv), 1st Baron Congleton. As a result, William Parnell assumed the name ‘Parnell-Hayes’ and Avondale was later the home of his grandson, Charles Stewart Parnell (qv). A memorial to Hayes's military service was erected, by his associate Capt. Thomas King, in the Church of Ireland church and graveyard in Rathdrum.