In the original woodland sheltering the Woodland Garden, the McDoualls planted species rhododendrons, transferring them as they reached maturity. The woodland was planted c.1800 mainly with hardwoods and, as they have matured, portions have been replanted with conifers. A burn runs through the area and has been used in the development of the garden. South of the burn, the ground rises steeply towards the former deer park of the policies. Some four hectares of this sloping ground has been acquired and has been planted with wind- tolerant conifers and some hardwoods. The original woodland is being replaced gradually and a wide variety of trees has been planted in the more open glades including several species of Eucalyptus and Nothofagus, as well as some fine Magnolia campbellii. Under these trees, the undergrowth is equally special and shrubs such as Olearias, the white flowering Eucryphias, and the evergreen Podocarpus grow in dense clumps along the hillside. Along the watercourse of the small burn is the Gunnera Bog where, amongst other water-loving plants, grow the gigantic leaves of Gunnera manicata, nearly two metres across.
The entrance to the Walled Garden area is through a simple iron gate. The original layout of the garden, indicated on the 1st edition OS map, appears complex. The original layout has been lost but the beech hedge and central wall remain from the original structure and, today, still serve to divide the garden into three main areas. Within the shelter of the walls the McDouall brothers transformed the Kitchen and Flower Garden into a sub-tropical haven. Throughout the 1920s they planted many tender plants outdoors which mostly could only be grown under glass elsewhere in the British Isles, except for perhaps the Scilly Isles. Wind is always a problem and so internal walls and hedges act as additional protection. On the south side of the internal wall there were glasshouses but these have been demolished.
The McDouall brothers wished to grow as many different plants as they could and so within the garden they created a range of different habitats. A square pond was built in one of the quarters of the south section and filled with water lilies. Other water margin plants such as Iris, Meconopsis and Hostas line the edge, planted in special beds. Two decorated urns on pedestals stand in the water which, in one corner, can be crossed by stepping stones. In the adjacent quarter there is the dramatic planting of tree ferns. Two species are grown, Dicksonia antarctica, planted by the McDoualls and D. fibrosa.
Just east of the pond is a small rock garden where sun-loving plants are planted. Constructed on a natural outcrop, the area uses the stream to connect a series of small ponds; moisture-loving plants and small shrubs grow along it.
On the south side of the internal wall grow sun-loving plants, whilst shade- tolerant ones thrive on the north side. Climbers on the south side include Abutilon megapotamicum, Campsis radicans and several species of Trachelospermum. The lemon scented verbena (Lippia citriodora), which usually has to be protected from frost if it is grown outside, does well here. On the north side, there are several Hydrangea species growing up the wall and two Schizophragmas, which look very like Hydrangeas. Along the same wall, Lapageria rosea hangs its great red waxy bells. To the east of the wall is the Tree Fern Mound covered with more Dicksonias, the tallest planted in 1913. This mound was reputedly created from the excavations from the ponds.
South of the mound is the peat garden where the McDoualls built low terraces of peat blocks for their collection of dwarf alpine rhododendrons and other ericaceous shrubs. It was here that the brothers pioneered the use of peat blocks to build small walls for acid beds.
On the west wall of the garden are the ruins of the old castle situated on an upper terrace and a series of smaller terraces all planted with tender plants and notable in some years for displays of Echium pinniniana. At the end of the border grows the tree Fuchsia excorticata, which has extraordinary greenish red flowers on old wood. Along the top terrace border grows a magnificent display of Diascias.
To the north of the beech hedge, which was planted c.100 years ago but was reduced by half in the 1940s, lies a more informal layout of island beds filled with shrubs and some half hardy herbaceous species. Originally there was a long pair of herbaceous borders here but these have gone. Magnolias and Eucryphias grow well and display their magnificent white flowers, the Magnolias in early spring and the Eucryphias in late summer. Throughout the garden there are long borders filled with unusual and colourful herbaceous plants and shrubs and at any time of the year there is always something in flower.