How green are my valleys

"It's about the pleasures of tweaking," Stephen Anderton laughs, explaining his philosophy of gardening. As one of Britain's most distinguished garden critics and biographer of the late gardening expert Christopher Lloyd (the book is due out next spring), Anderton is a big advocate of going over what you've already done, looking at it afresh, and working out the tiny changes that will bring it closer to perfection.

Anderton's tweaking is also a very social activity: one of his favourite phrases for it is "chewing the fat". He happily recalls fat-chewing sessions with Lloyd that would go on for five hours. "I know, because I've been rereading his diaries as I've been writing his biography, and he wrote it all down." Five hours of wandering around the garden, discussing what was going right, and where things could be done better. "There's nothing like doing that with someone you get on with," Anderton says with nostalgia.

Anderton also did a whole lot of fat-chewing last year while working on his latest book, Discovering Welsh Gardens (Graffeg, £18.99), for which he set out on a mission to find the liveliest gardens Wales has to offer. The book includes some classic Welsh gardens, such as Bodnant (the National Trust scheme there gets an energetic critique, with questions raised about the route walked), but the real fun comes when Anderton gets to young Welsh gardens, made by ordinary people experimenting with shape, texture and landscape. He has a personal soft spot for Tony Ridler's garden in Swansea, until now known only to aficionados. "It's the most refreshing thing. In the photos, it looks formal, but when you go round with the guy, he's so open-minded; and the garden is like a Rubik's Cube, you can shunt all the elements around to completely rearrange it."

Anderton has a thing for gardens such as these, made by people who don't come from what he calls "the gardening world". It's not hard to see why he connects with them, having moved with his family to Wales three years ago in pursuit of a life, he says, "where things get used up, where people fix things when they are broken".

"There are all these preconceptions about Wales," he adds, "but it's a fantastic climate for gardeners." And now I know where the good ones are, I just need to get myself there. And so from the National Botanic Garden at Wales (with its extraordinary Norman Foster glasshouse) to the Dingle in Welshpool – an exquisite woodland garden – Anderton's wonderful guide is enough to make me get on the internet and start looking for B&Bs.

Wonders of Wales: Pick of the plots

Veddw House Garden, Monmouthshire

Anne Wareham is famous for her hot-tempered attitude to horticulture on Five's Britain's Best Garden. But her own garden is a contemplative haven. Anderton says: "Some find it most attractively grim, more Silence of the Lambs than silence."

Plas yn Rhiw, north Wales

Gorgeous terraced garden with views out to sea, and an eccentric National Trust house to visit. Anderton says: "There is a feeling of an owner about to come out and potter and fix things personally."

Powis Castle, Welshpool

The grandest of 17th-century gardens with spectacular modern planting, including tropical borders, but in need of some love elsewhere. Anderton says: "Stand on the wilderness ridge and see what you think."