I once spent a short summer holiday in a walled Spanish garden. I was a guest of a wealthy banker who had bought a new villa, el Quinto Pino, in a new development in the scrabbly slopes above Malaga. My only obligation during the day was to ensure my lounger, and thus my pasty skin, was in the shadow of the only bougainvillea on the patio. Every evening my task was to hosepipe the gaudy emerald ‘lawn’ inside the concrete walls, toughened grass as comfortable to walk on as cactus. Twice a week a tanker wheezed up the hill and filled the villa’s cisterns. In every sense it was gardening against the gradient.

My host’s thirsty square of green wouldn’t get a mention in Monty Don’s lavish new book featuring 40 glorious examples of how to make the best of Spanish sun, drought and thin soil. Strolling through the grounds of a former monastery, Las Nieves in Toledo, he remarks that he is often asked the question ‘what is a Spanish garden?’ and suspects that a clear true answer is as unachievable as defining Spain itself. Yet, inspired by the clipped bay, cypress, myrtle and box hedging of Las Nieves he immediately declares it the essence of Castilian gardening – no flowers, no fragrance, just green, everything reduced to its elemental bones.

Green, in its infinite tones, is the dominant palette of the sumptuous photographs taken by Derry Moore on their horticultural pilgrimage. If you were unfamiliar with glaucous green at the outset you will recognise it instantly by the end. Starting in the rain at the baroque Pazo de Oca in Santiago de Compostela and meandering via Bilbao, Barcelona and Mallorca, Monty and Derry end up at Las Duenas in Seville, household of the Dukes of Alba, a place of exquisite golden-walled beauty, shaded courtyards, fountains, ornate orchards and palms.

In bygone times you needed aristocratic and royal wealth to engineer the unforgiving landscape, install wells and manhandle mature olives into a pleasing line. Old hunting estates and posh vineyards in the Douro Valley add repetitive patterns and make a virtue of the liminal space between farm and garden. At Pedralbes Monastery they have revived the practice of growing only pre-Colombus crops. Some of the magnificent city parks, most notably the Retiro in Madrid, if not the austere symmetry of El Escorial, are now enjoyed by millions.