Glenarn is a private garden largely created and originally made famous for its collection of species rhododendrons by the Gibson family. Established in the 1920s and 30s the garden lies in a protected hollow with a steeply sloping glen running its length and providing shelter for large-leafed and tender rhododendrons. Early in the spring, tall Asiatic magnolias create dramatic interest while other plants such as crinodendrons, eucryphias and acers give colour at different times.
Later in the summer, the large rock garden, built round the old quarry and natural rock outcrop, provides a variety of habitats for smaller plants such as meconopsis, primulas, paeonias, dwarf rhododendrons and many bulbs in season. This area has recently been deer fenced.
In the centre of the garden below the greenhouse, there is a working vegetable and fruit garden which provides produce for the house.