Architectural Features
Keillour Castle, listed category C, was built in c.1877 to the design of Andrew Heiton. A stone bridge spans the Keillour Burn to the east of the Castle. The Knox Finlays brought up several pieces of stonework from the Houses of Parliament (by ship to Dundee) which are incorporated throughout the garden, one of which, a Tudor Rose is incorporated in a retaining wall near to the pathway down to the 'Snib'. A sundial stands on the lawn to the south of the house.
Woodland Garden
The woodland garden was laid out beneath an established canopy of beech and of ornamental conifers which had been planted c.1880. The woodland canopy is important for the shelter which it provides from the prevailing wind. Clearance of timber in 1947 exposed fine specimens of Douglas fir, Norway maple and Wellingtonia which remain today. Many other conifers planted in the late Victorian period were measured by Alan Mitchell in 1962. The main south drive, lined with Japanese maples and shrubs, passes along the east side of the woodland garden en route to the Castle. A footpath off this drive leads to a lookout point where a fine view of the Keillour Burn waterfall and bridge can be gained. The south drive joins the east drive and turns west across the bridge and up to the Castle. Climbing shrubs have been established on the walls of the Castle, including Parrotia and Wisteria. Daphne blagayana and other groundcover shrubs, many of them tender, clothe a bed along the east wall. Lawns extend from the house to the east and south. The south lawn extends to a cotoneaster hedge, beyond which are shrub borders centred around a huge Wellingtonia. To the west of the house, a pathway leads north down into the gorge of the Horn Burn into 'the Den' where giant Rhododendrons, Magnolias, Sorbus and maples are grown beneath the woodland canopy, while a variety of Erythroniums and other groundcovers have become established. This area appears natural, and Sir George Taylor recorded that it is strongly reminiscent of the gorge country of South-East Tibet, an impression entirely created by the imaginative planting carried out by the Knox Finlays. The area has extended into the 'Nursery' marked on the 2nd edition OS map of 1901. From the lawn on the east side of the house, a pathway leads down to 'the Snib', where the banks are so steep that ropes had to be tied around the waists of gardeners when the Rhododendrons, Azaleas and other species were planted. Primulas and other waterside plants are naturalised on either side of the burn. Good views of this area are obtained looking south from the bridge. Looking north from the bridge, the gorge area is known as 'Hell'. Here, on peat terraces on either side of the burn, various unusual Primulas have been established including P. griffithii, P. edgeworthii, P. gracilipes and P. sonchifolia. The fast flowing water of the burn is utilized to divert water by means of a hydraulic ram put in by Major Knox Finlay to pump the water up to the water garden south of the bridge at the upper level of the garden next to the drive. Here Magnolias, willows, Eucryphia, Azaleas, Rhododendrons and Deutzias, surround a large pond, at the edge of which grow irises including I. delavayi, I. sibirica and I. laevigata, Lysichitums, Meconopsis, Hostas, Rodgersias, and candelabra Primulas, among others. Between the water garden and the bridge, overshadowed by trees and shrubs, Gentians, Trilliums, and Cassiope are among the many plants which have been established as groundcover. Even Oiphanidesia gaultheriodes is nurtured here under glass. North of the house, beyond the drive, is the rock and scree garden which has been extended on to the former tennis court. Here, numerous botanical treasures are grown including Lilium henrickii, the rarest lily in cultivation, and Lilium lankangense, a favourite of Mrs Knox Finlay, as well as many Meconopsis. Keillour is nationally renowned for its collection of plants from the Lillaceous genera, particularly Nomocharis, Notholirion, Cardiocrinum and Primula, especially those from the petiolaris section. The plants within each area were documented in a list prepared by the Royal Botanic Garden, Edinburgh. The Knox Finlays received seed from original collections by Ludlow & Sherriff, and have over the years propagated and distributed it to other plant collections and gardens.
Walled Gardens
The kitchen garden is situated to the north of the Castle between the old tennis court and Green of Keillour. Access to the kitchen garden is by way of a flight of stone steps which were originally the front door steps of Balgowan House which was demolished in 1948. The garden is walled on two sides, open to the east where it dips steeply downwards to the shelter planting above the Keillour Burn, and bounded on the south by a well trimmed, 17' high, yew hedge. Part of the garden has been laid down to grass due to a reduction in produce requirement from the house but most of the area is still well stocked with fruit and vegetables grown in compartments which are separated by trellises trained with Clematis orientalis and by herbaceous borders.