African Odyssey: a horticultural tour of Marrakesh

Does a city ever really need lawns? That's a question posed by Angelica Gray in her new book Gardens of Marrakesh. In preparation for reading it, I've been trying to summon up images of Marrakesh that aren't straight out of desperate cliché. So far I've done badly. Keith Richards and Anita Pallenberg much the worse for wear; Yves Saint Laurent wiped out and lying low on some cane furniture after some of the 1960s' most fabulous fashion shows. That funny but totally Californian song by Crosby, Stills and Nash. A hotbed of drugs, souks, rally cars and exotic carpets…

It's amazing just how much clichéd rubbish on the subject of the great Moroccan city can be floating around in a single human brain. Luckily, I am now equipped with completely fresh ideas on the subject to shoo out Mick and Bianca. Just flick through a copy of Gardens of Marrakesh and immediately you're taken on a nosy trip around the town by Gray, a guide who knows every cool, fountained courtyard and elegant green space.

A garden designer whose parents were Anglo-Indian Londoners and who chose Morocco as a halfway point to live, Gray clearly knows the city inside-out, down to being able to comment on park litter and planning regulations like an avid member of the local neighbourhood watch.

She is also a careful scholar of economic history, cataloguing the flow of French metropolitan money to and from Marrakesh: the polo-playing, saddle-making millions of the Hermés family (and on a more modest scale, two history teachers from Toulouse who inherited a mysterious house and garden, whose deeds were found inside a fig tree).

And, finally, she's happy to do postcolonial, posing that thorny question of whether those European-style lawns really do belong in a city that is only now discovering its own horticultural heritage.

Set against a dramatic jagged skyline provided by the High Atlas Mountains, the city's views are safeguarded by local old town laws forbidding buildings taller than a palm tree (minarets are excepted). Which is convenient, because Marrakesh is full of gardens. In the very heart of the city, ancient royal palace walls and legendary hotels alike enclose dramatic green spaces. Utterly historic, grand and beautiful, but none stands still.

The Mamounia Hotel, for example, has hosted visitors from Charlie Chaplin to Nelson Mandela, and after they were remodelled in 2009, the gardens now contain that essential 21st-century chef's accoutrement – a potager for local produce.

Outside the central medina – the old, fortified historic district – there's the Agdal, a vast Islamic Versailles, while to the north-east of the city, 180,000 palm trees make up the Palmeraie, a green sward that runs all the way to the river Issil. And to the north-west, the famous souks shelter old-fashioned riads – townhouses with shaded gardens behind protected walls. Here are the blue-and-white star tiles and intricate pillars you'd expect of Islamic architecture and the delicious rammed-earth pink of walls that is entirely local. In every corner of the city, fantastic gardens await.

Which brings us back to Yves Saint Laurent. I have a particularly vivid image about this one because I've just finished reading Alicia Drake's almost terminally controversial account of Paris fashion in the 1970s, The Beautiful Fall. It's a fabulous tale of kaftans, muses, mannequins and, um, leisure drug-taking, which details Saint Laurent's passion for Marrakesh.

Born and brought up in Algeria, Saint Laurent always hungered for the warmth and light of North Africa, and with partner Pierre Bergé he visited and eventually acquired the house and gardens at Jardin Majorelle. A deep Klein blue is the signature colour of the place, uniting pools, walls and floors in a richness totally at odds with the desert dryness of the air. The garden was originally made by the early Modernist Jacques Majorelle, fleeing Paris in wartime (the First World War, that is), but it was Bergé and Saint Laurent who eventually restored it, with the help of local ethnobotanist Abderrazzak Benchaabane. Twenty gardeners work full-time today to maintain this astonishing vision. And if there's one lesson Marrakesh teaches, it's that in a world of blues and oranges and palm leaves, there's no need for lawns at all.

'Gardens of Marrakesh' (£20, Frances Lincoln) is out on 4 April