Our gardening expert Pattie Barron has had exclusive early access to the show to witness the designers, carpenters and craftsmen add the finishing touches to their plots. Here, she reveals her top six.

Herb expert Jekka McVicar’s petite, perfectly formed courtyard garden, A Modern Apothecary, could be dropped neatly into any small outdoor space, so it’s no surprise that it will be reinstated in the garden of the hospice at St John & St Elizabeth in north London, for patients and visitors to enjoy as a restful and fragrant retreat.

Every plant here has a purpose, says McVicar. Hops that frame the entrance archway are an aid to sound sleep, while pears that feature in the low stepover fruit trees help regulate Type 2 diabetes. Even the willow that backs the benches is a source of salicylic acid, used in aspirin.

A trickling water fountain sits in the centre of an aromatic thyme carpet that is surrounded by a lavender-lined pebble path for the brave to walk on barefoot for an impromptu reflexology treatment.

No garden at Chelsea is as welcoming as the RHS Greening Grey Britain Garden for Health, Happiness and Horticulture, designed by the effervescent Ann-Marie Powell, a Chelsea veteran who imbues all her gardens with energy and vibrant colour.

The central porcelain path that, exceptionally, visitors to Chelsea will be able to walk down — this is a community garden, after all — has been carved with greetings in the top 10 languages spoken in the UK.

“I wanted to appeal to everybody, so they feel a sense of ownership,” says Powell, who upcycled a shipping container into a bright orange potting shed and enterprisingly pitched a potted kitchen garden on its roof.

Enjoy a detailed tour of this garden in next week’s Homes & Property, and when the show is over, you can visit the garden at its permanent location in Angell Town, Brixton.

It might look like the embodiment of an English country garden, but give it time — 15 minutes on the hour, to be precise — and the turret of the tower pops open, the flower beds revolve, the topiary twirls and those ground-floor window boxes rather alarmingly rise to the second storey.

“It’s an English country garden on acid,” says showman Diarmuid Gavin of the Harrods British Eccentrics Garden which has, he adds, more electronics than a space shuttle.

It also has sublime planting, the kind we’d all love at home, because, he says, this garden has to work on its own merits, without the bells and whistles. And it does, beautifully, but he has had the help of another Irish gardening tour de force — Helen Dillon worked on the planting plan with him.

Cleve West’s quietly sublime garden for M&G, Chelsea’s sponsor for the seventh year, gently draws you in, and, after a few moments, mesmerises.

Inspired by West’s memories of Exmoor National Park, where he spent time as a teenager, the naturalistic planting is primarily woodland.

Oak trees form the boundaries and the structure comes from sandstone boulders and rocks quarried in the Forest of Dean. The path is a metaphor for West’s journey into garden design, starting with rough stone and becoming smoother as it reaches the central, sunken terrace and pool.

“This garden is a celebration of the beauty of mathematics,” says designer Nick Bailey, who moonlighted from his main job as head gardener of the Chelsea Physic Garden to create this ambitious and beautifully executed landscape.

The Winton Beauty of Mathematics Garden comprises plants from around the world with mathematical patterns, shapes and symmetry in their formation.

The key element that runs through Bailey’s Chelsea garden is a copper band, inscribed with a series of plant algorithms, that represents a stem rising from the soil and, as it swirls around the garden, becomes a bench, a banister of a sweeping staircase and finally, at its summit, a belvedere that drips with plant species.

Who wouldn’t want to sit beneath its leafy canopy, taking in the astonishing views?

Gardens at Chelsea owe much to craftsmen, from carpenters to metalworkers. Case in point is A Garden for Yorkshire, inspired by the medieval Great East Window at York Minster.

The window is nearing the end of a 10-year restoration, and is symbolised in a magnificent garden building with stained-glass panel, courtesy of York Minster’s stonemasons and glaziers, using 600 years of historical skills.

“My concern was how to get the colours of the window into the planting,” says designer Matthew Wilson. “But what holds all the colours together are the white flowers of Viburnum plicatum Mariesii and Orlaya grandiflora.”

He has gone with an ecclesiastic theme of peach rose York Minster and white rose Winchester Cathedral, but because he’s from Kent, couldn’t resist including the delectable toffee-tinted iris Kent Pride.