Dyffryn House (nprn 18592) is a large mansion in French Renaissance and English Baroque styles situated in gently rolling countryside approximately 2km south of the village of St Nicholas in the Vale of Glamorgan. Although a park and gardens have existed around Dyffryn House since at least the eighteenth century, the site is best known for its Edwardian gardens, considered to be the grandest and most outstanding example in Wales, laid out by the landscape architect Thomas Mawson in collaboration with the owner Reginald Cory an exceptionally talented horticulturist and plantsman. 

The walled garden lies west of the house and pre-dates the Mawson landscaping. It may well date back to the sixteenth or seventeenth century, contemporary with the earlier house on the site. The garden lies on a south-east facing slope. It is rectangular, long axis north-east by south-west, and consists of one large compartment and a smaller one to its north-east. The garden is enclosed by roughly-coursed stone walls standing to their full height, variable but up to 4m high. Running the full length of the north wall is a modern lean-to glasshouse. There are ranges of buildings along the exterior of the north and east walls.

The garden is shown in its present form on the tithe map of 1841 and 1878 Ordnance Survey map, with two compartments and a small glass house in the middle of the north side of the main one. By the end of the nineteenth century a huge glasshouse had been erected along the north wall. This probably dates to after 1891 when Sir John Cory bought Dyffryn. Until the 1930s it housed Reginald Cory's collection of tender plants.

House and gardens lie within a small park (700370) which was reduced from 1905 onwards for the creation and expansion of the gardens. 

Sources:
Cadw 2000: Register of Parks and Gardens of Special Historic Interest in Wales, Glamorgan (ref: PGW(Gm)32(GLA)).
Ordnance Survey first-edition six-inch map, sheet: Glamorgan XLVI.11 (1885).
Ordnance Survey first-edition six-inch map, sheet: Glamorgan XLVI.11 (1901).  

RCAHMW, 15 July 2022