Walled gardens were a necessity for any great house in a northern climate in the eighteenth and nineteenth century, as a high wall of stone or brick helped to shelter the garden from wind and frost, and could create a microclimate in which the ambient temperature could be raised several degrees above that of the surrounding landscape.

To allow both the upper and lower parts of the garden to be flat and level at different heights, it was necessary to bank up the earth on the higher northern side (away from the main house), behind a retaining wall about 16 feet (4.9 metres) high, and 3 ft 3 in (1.0 m) thick, which runs the entire length of the north side of the garden.

[citation needed] A building containing a hothouse was built into this wall in 1761 by John Murray, 4th Earl of Dunmore.

The upper floor, which is at ground level when approached from the raised northern lawn, contained two small cottage-like apartments, or "bothies", for the gardeners.

The upper-floor pavilion or summerhouse with its pineapple-shaped cupola and the Palladian lower-floor portico on the south side were added after Murray's return from Virginia.

The south (ground floor) entrance takes the form of a characteristically Palladian Serliana archway, incorporating Tuscan columns.

Visitors who step through this archway and into the vestibule below the pineapple face an elaborately framed doorway, flanked, on either side, by pairs of painted wooden Ionic columns, carved with great care, which display perfect fluting and even architecturally correct entasis.

[6] Above the Serliana arch is inserted a “later and clumsier,”[7] panel bearing a relief carving of a heart charged with a cinquefoil and inscribed with the motto Fidelis in Adversis.

Each of the curving stone leaves is separately drained to prevent frost damage, and the "stiff serrated edges of the lowest and topmost leaves and the plum berry-like fruits are all cunningly graded so that water cannot accumulate anywhere, ensuring that frozen trapped water cannot damage the delicate stonework.

"[3] Despite the unconventional design and the mix of architectural styles, the effect is harmonious because the pineapple and the portico are made of the same stone (ensuring a single colour from top to bottom) and are of a consistent width.

Architects, artisans and craftsmen adopted the pineapple as a motif, sculpting it into gateposts, railings, weather vanes and door lintels.