The old gardens at Drenagh extended to nearly 70 acres at the end of the 19th century. There were long meandering walks through Beech woods and along the Castle Burn; a Rhododendron Glen filled with rare plants collected in China, Nepal and Bhutan; a formal Italian Garden dominated by a sandstone balustrade reminiscent of the Villa d'Este; an English Garden planted in the manner of Gertrude Jekyll; a conifer arboretum; a fabulous 4 acre walled kitchen garden and a cricket pitch in front of the North facade of the house.

More recently a Moon Garden has been created in the last remaining building from the first McCausland house, Fruithill. It is an entirely white garden dominated by shape, form and scent and tries to capture the tranquillity of the oriental garden style.

The beauty of the Drenagh Gardens has been perfectly described in the book ‘The Hidden Gardens Of Ireland, Where to find them’ by Marianne Heron.

‘Imagine a secret enclosure, filled with the glimmer of white flowers and silver foliage, with a curious circular window framing a lake-like vista of lush growth and stately trees. This is the effect of the Moon garden, a perfect hidden place perched on the edge of an escarpment overlooking a fine nineteenth-century arboretum.

The next significant additions to the gardens were made in the 1960s, during Lady Margaret McCausland's time, by the Canadian landscape artist Francis Rhoades. An English garden, in pink, blue and silver with a rose and clematis arbour, a water garden and a circular azalea garden beside the Italian garden were her creations. The Moon garden, with its oriental style loggias, was created from part of an existing building where bee boles, used to house bee skeps, are an intriguing feature and the circular steps leading down from the Moon window are flanked by weeping medlars.’