I confess here and now to annihilating one or two with my ray gun — a magnifying glass focusing the sun's rays. It's quite a confession and I apologise. The garden was also the perfect location for the action films I made with my Standard 8 cine camera. Quite a few toy cars were crashed and blown up with fireworks in the pursuit of my art.

Thankfully, as I grew older, my activities in the garden became less destructive and more productive.

I discovered gardening in the garden. Who'd have thought?

But I'm convinced that if you spend enough time in a garden, you soon become a gardener. I noticed that plants grew and flowered and set seed, and that those seeds turned into new plants. Bits of plants stuck into the ground or pots of soil became plants too. It was all rather fascinating.

Then I discovered seed catalogues. I realised I could grow almost anything from seed, and I set about proving it. I remember growing loofahs, of all things. They're a sort of marrow-like plant, and I discovered I could grow them quite easily in the greenhouse my father had built for me.

I grew flowers, fruit and vegetables, and before long I'd taken over my parents' garden. I think they were quite relieved. They could enjoy it without having to do all the work, and I had the freedom to do whatever I wanted. A perfect arrangement.

Gardening had become my passion, and my parents encouraged me to pursue it. I went on to study horticulture and eventually made it my career, first working with plants and later making gardening programmes for radio and television.

But gardening was never just a job. Wherever I lived, I needed somewhere to grow things.

When I moved to London to pursue my television career, my only outdoor space was a balcony outside my third-floor flat. Undeterred, I filled it with pots of plants until there was barely room for anything else.

Then I moved in with Paul, my partner. He had a house with a little garden. He was quite a keen gardener himself but, rather like my parents, seemed perfectly happy to let me take over.

Before long I'd filled the garden with wonderful plants, including olives, a grapevine and a tree fern. I built a pond and a greenhouse, and somehow we managed to squeeze it all into a relatively small space. It became our own little sanctuary in the city.

A few years ago, Paul and I moved to Cape Town, accompanied by Daisy, our fox terrier.

Our garden here is rather different. We're on the slopes of Table Mountain, and the land falls steeply from the road at the top down to a stream at the bottom. Gardening involves a great deal of going up and down steps, creating terraces and finding ways of making the most of the slope.

The climate is different too, of course. After years of gardening in Britain, the speed at which things grow here still amazes me. For a now older gardener, a subtropical climate suits me down to the ground. There's less waiting around for things to happen, although the weeds seem equally delighted with the growing conditions.

We've already managed to create a garden that feels quite lush and established, and it's still evolving. I doubt I'll ever consider it finished. There's always something to change, something to move, or another idea to try. I think that's part of the pleasure.

After a lifetime of gardening, studying horticulture, teaching, designing gardens and making gardening programmes, I've occasionally wondered what it is about gardening that still gives me so much pleasure.

I think it's a number of things.

First and foremost, it's probably creativity. I love making spaces, arranging plants and creating my own little bit of nature. A garden is never really finished, and perhaps that's what makes it so absorbing. You can have an idea, put it into practice and then watch nature have its say. Sometimes the results are exactly what you imagined. Quite often they're not.

Then there's the nurturing. I enjoy trying to give a plant the best possible conditions in which to grow and hopefully thrive. There's something enormously satisfying about raising a plant from a seed or a cutting and watching it develop into something quite wonderful.

But perhaps the simplest pleasure is just being there.

I love wandering around the garden, seeing what's changed, smelling the flowers, watching the bees on the lavender, the birds in the trees and the insects going about their business. I can spend a ridiculous amount of time doing very little, although I prefer to think of it as observing.

And after all these years, I still find things that fascinate me, just as I did when I was a child.

There's no zapping these days, not even with chemicals.