Reluctant gardener: Author David Hessayon, 80, says tending plants is a job rather than a hobby

As author of the Expert series on how to make things grow, David Hessayon is the bestselling non-fiction writer in the world.

But despite teaching millions how to get the best out of their garden, he admits that tending his own roses and shrubs no longer gives him pleasure.

'I'm fortunate enough to have all of the plants featured in my books,' said the 80-year- old multi-millionaire, who is known as the Doc and lives in Essex.

'But I feel that I know too much for it to be therapeutic. I can see problems about to happen. And so, in Who's Who, I don't quote gardening as my hobby. It isn't. It's my job.'

Having sold more than 50million books on horticulture, including his latest best-seller on vegetables and herbs, Dr Hessayon is now to publish one about cats.

In a rare interview, given after he was awarded an honorary science doctorate by Leeds University where he took his first degree, he talked of his early life as one of five children in Salford.

From the age of five he would help his Cypriot father, Jack, a watchmaker, to cultivate a few colourful reminders of the country he had left behind.

'The love of his life was this little plot with four square beds, eight lilies and some hydrangeas,' he said. 'From a very early age, it was my job, with him, because his health wasn't good, to look after this small plot.

'Like lots of kids, it wasn't so much the love of the garden, but that your father's love was so terribly important. And that's where I really learnt my art.'

David Hessayon (right) with Melvyn Bragg at an honorary degreee ceremony at Leeds University

He also cited the early loss of his mother, Lena, when he was six, as a major motivation behind his success. 'There was some research which suggested that many self-made men share the fact that they lost a parent before the age of ten.

'A kid says in his mind, "It's a bloody unfair world and if I'm not smart, things could turn out even worse". I think that's true for me. I knew that things do happen, that it's not a bed of roses and that you're going to have to fight to survive. Life has got a cruel edge.'

Dr Hessayon studied botany and chemistry at Leeds University before achieving a PhD from Manchester University in soil science-After meeting his U.S-born future wife Joan in Paris in 1949, he was so determined to woo her that he moved to Missouri to work for her father's newspaper.

He later became managing director of Pan Britannica Industries, the makers of Baby Bio.

Dr Hessayon said it was seeing his bound PhD document which made him decide to become an author. 'It was green with gold letters on it. It said DG Hessayon, and I thought, "This is what I want to do".

'The real secret of my work is that people feel at ease with them. People say they are the kind of books which they could have written themselves, which is really the best compliment.' Half of all British homes are said to have at least one Expert book.

Dr Hessayon's wife, a romantic novelist, died in 2001, after which he set up the Joan Hessayon Award for new writers in the genre. He enjoys a modest lifestyle and said the values of his early life are still important to him.

'We were street children. There were so many of us in such a small house that we spent all our time in the street. But there was a terrific sense of community. If you got hungry then someone would feed you.

'It was the old rags to riches story. You'd nowhere to go but up and that's a great thing in life.'