Andy Goldsworthy: 'Lying down in Times Square in the rain is bound to attract attention'

All your work is site-specific, much of it ephemeral [Goldsworthy, a featured artist at the forthcoming Folkestone Triennial, uses everything from flowers and twigs to icicles and rain in his work], so the beach and seashore of Folkestone is your kind of habitat. Are we talking castles in the sand?
People might be surprised by my choice of locations – I was shown the park, the shore, the cliffs, but I chose semi-derelict buildings in the town, specifically an empty shop and a staircase in a house, which I have covered in clay. For the Triennial I've worked with clay at both its most raw and its most refined. Grey clay from the beach and white china clay from suppliers.

Why clay? Is it a well-behaved material?
The raw clay is obviously relevant to Folkestone, but china clay also has a presence there in the crockery used in homes, cafes and restaurants. Combined, I hope they are a reminder that the cup we drink from and the buildings we live in are nature.Clay can be well-behaved and easy to work. Yet it has such a powerful impact on the landscape: it reveals its more unpredictable qualities as it dries, and this process interests me most. Perversely this is also the time I cannot touch it. I've placed a layer of clay over the stairs of one building and the shop front window of another. As the clay dries it reacts to what lies beneath. The shape and form of the steps are drawn in the cracks and fissures. It acts like a poultice, reflecting the structure beneath it.

Does working with natural objects give you a greater sense of the planet's permanence, or of its fragility?
Both. Nothing lasts. We all have to deal with loss. When I make something, in a field or street, it may vanish but it's part of the history of those places. In the early days my work was about collapse and decay. Now some of the changes that occur are too beautiful to be described as simply decay. At Folkestone I got up early one morning ahead of an incoming tide and covered a boulder in poppy petals. It was calm and the sea slowly and gently washed away the petals, stripping the boulder and creating splashes of red in the sea. The harbour from which many troops left for war was in the background. The whole process was recorded for a time-lapse video that will also be shown at Folkestone.

Do you become emotionally involved in the material you work with, whether permanent or transient?
All materials have the ability to provoke a wide range of responses. Working with leaves can prime me to work with stone and vice versa. There is an intensity achieved through touch. I like to work with my hands. I need the contact and shock of hand on materials.

You surely have to be fit, strong, healthy, with good eyesight and good nerves to be Andy Goldsworthy. What are the risks?
One of the most dangerous places I work is near where I live. A river has cut out a small gorge where I go in winter to work with icicles and ice. Often I'm there just before dawn when it's coldest, working in the dark on icy rocks. I've been making works with my body, a practice that I often did in the 1970s and have continued since in the form of rain shadows. Last year I made a work that involved walking through a mangrove swamp in Gabon, Africa. The swamp was soft underfoot and the roots easy to crawl through. Shortly afterwards I made a similar work in a hedge in Hampshire, from which I emerged cut and bloodied. Who would have thought that an English hedge would be more dangerous than an African swamp?

Are you a one-man show?
There are two sides to my work: the installations, which are usually commissions and involve other people, machinery, state of the art tools. Then there's the ephemeral work I do on my own, without tools. I go to a place and never know what I'm going to do. Art can show you what is there. I'm always amazed how blindingly obvious things are which I'd never noticed.

The second of four children, you grew up on the edge of a city. Your father was a mathematician. How did these factors influence you?
I grew up five miles from Leeds in a new house in the suburbs. At first we were surrounded by fields and woods. Then they were built on. I felt angry, but realised my house had also once been fields. I always felt that in some way they were still there – just below the surface. As for my father, I'm no mathematician but I often feel his presence, when I'm trying to work out how to make or build something.

Do you still see yourself as an outsider – that old label "new age whimsy"? Is being part of the Folkestone Triennial a mark of acceptance?
Whether I'm accepted has never been of huge interest, or motivation, for me. I rarely show in Britain. Currently I'm working in Brazil, Canada, Spain, America, France – so it's good to do something here.

You must be an optimist to make art that vanishes?
Working with change is to also work with the future. The work doesn't necessarily predict what will happen but does embrace change, whether it be growth or decay. This is in itself an act of optimism. The other day I made something out of puddles and leaves in a Glasgow car park. Someone drove over it. I made it again. The same person drove over it again on their return but apologised for doing so. That was pleasing! Why should anyone say sorry to someone messing around with leaves and a puddle? Luckily I'd finished and was in the process of photographing it. As a result I have images of the completed work, the car driving over it and the surprisingly interesting pool of green leaves and black dirty water left afterwards.

You must get some funny looks?
[Loud laughter.] My work is a very personal and private act but usually made in public places. Sometimes I feel embarrassed but I have to get on with it. Lying down in, say, Times Square, New York in the rain waiting for my shadow to form is bound to attract attention. In fact New York is one of the easier places to lie down in the street – no one really cares.

You live in south-west Scotland. Will the referendum outcome make a difference to you?
I've now lived in Scotland the majority of my life. My children have been born and brought up here. My studio is the fields and farms around where I live. Working with the land is to work alongside its people. The social nature of landscape has a profound effect upon my work. Will this change because of the referendum? I don't know. I came to Scotland in 1986 – an artist and Englishman in a small rural village – possibly two reasons to be treated as an alien anywhere. In Scotland I've met with not just tolerance but real engagement. That's what keeps me there.

The Folkestone Triennial runs from 30 August to 2 November