The Wilderness was laid out in the time of the 2nd Earl and, in keeping with prevailing fashion, was informal in character with meandering paths. It was originally planted with native trees and shrubs, such as oak, holly and yew, which now provide the shelter and protection for the Gardens' rhododendrons, magnolias and camellias.

The Wilderness provides a habitat for many kinds of birds including rareties such as nuthatches and hawfinches.  Several species of owls, woodpeckers, sparrowhawks and kestrels are also frequently seen. 

Over 200 different kinds of fungi have been recorded in the grounds within a single year, including stink horns and rarely seen wax caps. Two of the most spectacular are the giant puff ball, whose fruiting bodies can measure up to 60cm/2ft across and the beef steak fungus, which looks like a piece of raw liver.

Trees and plants to be found in the wilderness include: Eurcryphia, Hydrangea and Cyclamen (late summer flowering; Acers, Limes, Hydrangea, Birch, Hornbeam, Oak, Sorbus, and Beech (autumn colour); Tillia x europaea (European Limes); Sequoiadendron giganteum (Wellingtonia); Taxus baccata 'Fastigiata' (Irish Yew); Veteran tree - Castanea sativa (Sweet Chestnut); and venerable trees - Oaks, Beeches, Sycamore, and Monkey Puzzle.