The Artist's Garden, on the roof of Temple Tube Station

I’m on the roof of Temple Underground Station, part of a group of assorted journalists, artists, architects, engineers, PR people, horticulturalists, and arts admin staff, listening to a benign-looking white-bearded man seated on a fold-up garden chair, addressing us through a microphone.

It’s sunny, but fast-approaching gloomy clouds threaten rain. In the background the River Thames, and beyond it the jaggedy glass-and metal high-rise spires of 21st century London.

The man is sitting in front of a smaller construction, made of the same materials, a garden greenhouse, with what looks like a mini-henge of standing stones within, white lines representing constellations daubed on the panes.

“The greenhouse,” he says, “is like a temple. A place of devotional engagement with nature. That’s where the magic happens.”

The man is Tony Heywood, one half of the artist-couple Heywood and Condie (the other being his partner Alison), whose art defies pigeon-holing. Land artists? Not quite. Artist-gardeners? At a pinch. Three-dimensional landscape artists? Getting there. Horticultural installation artists? That’s it! Maybe.

The pair have, for 30 years, been collaborating on a line of work whereby they create installations from natural materials, crossing genres, incorporating elements of film and video, painting and sculpture, performance and science. His background is in horticulture and anthropology, hers in botany and zoology. Their latest work, in The Artist’s Garden on the aforementioned station-rooftop, is called Through the Cosmic Allotment.

The greenhouse is one of four, arranged in a semi-circle, with different materials inside, with symbols painted onto the panes, part-obscuring them from view. Heywood continues his talk, explaining what they represent. One contains rotund bejewelled forms, magnified embodiments of micro-organisms, ‘blinged up to the level of hypervisibility’: the beginnings of life on earth. Another has pink and yellow neon-hued scholar’s rocks, to facilitate meditation on the paradoxical complexity/simplicity of the universe. The stone circles in the third stand for man’s attempts to understand the cosmos. The fourth greenhouse, virtually empty apart from a carpet of tiny round stones, with a single mini-pebble seemingly floating in the air, represents ‘a sub-atomic particle within a quantum field, life at its greatest level of connectivity and simplicity’.

The secrets of the universe, and man’s place within it, loaded into four greenhouses on a rooftop in central London. This is a show with some scope.

“We live in a virtual age,” concludes Tony, competing with the sound of a team of workmen operating their pneumatic drills in the high-rise development overlooking the garden, “in which we are increasingly distanced from real nature. We increasingly see nature through symbols, and screens.”

Funnily enough, I started my day in my own greenhouse in Sussex, digging out rhizomes: stubborn mud is still darkening the edges of my fingernails. Over a glass of wine, after his talk, I chat with Tony about soil, about weeds, and about whether or not nature seen through a prism of distorted reality created by Shamanic meditation is more real than nature viewed through ‘normal’ eyes. “In the right circumstances you can go beyond connecting with nature,” he says. “You can immerse yourself in it.” And then: “What we’ve created here is a form of magic realism.”

The clouds have disappeared, the sun beats down. I flip my glasses off the crown of my head, over my eyes. This event is a finissage, of sorts, the greenhouses come down on May 23rd. I recommend a visit, if you’re in the vicinity. If it didn’t exactly blow my mind, it certainly opened it to the paradoxical duality of simplicity and complexity within the infinite reaches of the cosmos. And you can’t say that of every art show.