Trelydan Hall (nprn 21424), near Guilsfield, is an ancient site dating from at least the medieval period when the surrounding land lay within the demesne of Strata Marcella Abbey. The history of the surrounding grounds is otherwise uncertain (700257).
A roughly rectangular garden surrounds the house on all sides on ground sloping from west down to east. Although the history of garden development here is unclear the form of the present garden is typical of the period 1890-1920. 

The garden is bounded on the west by a group of old yew trees (possibly ornamental plantings) and on the east by a small brook/water channel at the bottom of a sloping lawn.
To the west of the house a group of old yews stand near the garden boundary, while a tree-planted lawn slopes down to a small brook/water channel on the eastern boundary. The main block of the garden, to the south, is divided for 50m by the straight approach drive bordered by low clipped box hedges, through an area partly enclosed, on the east and south, by a red brick wall surrounding a lawn with herbaceous borders (21427), and a modern glasshouse and bothy/potting shed. Opposite, shrub and conifer island beds dominate a second lawn. Nearby, a dammed linear pool feeds the water garden which runs across the top of the garden, south of the house front. The water garden centres around a sunken canalised stream set with weirs and rocks. Stone-flagged paths run on either side of the stream with steps connecting to the garden and entrance court above. To the north of the house there is a large circular lawn with nearby shrubberies.

The Hall is a mainly Tudor and Jacobean house and it is assumed that there would have been a garden here at least from the seventeenth century but no archive evidence for it has been found. Today the features which date from about that time are the yews to the west of the house and the garden wall. However, it is unclear if the wall ever continued around to the west of the garden.

Source:
Cadw 1999: Register of Parks and Gardens of Special Historic Interest in Wales, Powys, 250-53 (ref: PGW (Po)2(POW)).

RCAHMW, 17 June 2022