Last year, doubtless realising he was the jewel in its crown, the RHS gave Wilson, 42, a special role: head of gardens creative development, which means he is responsible for developing new landscapes in all four of its showcase gardens.
© GAP Photos/Marcus Harpur
His revolutionary no-dig, no-feed, no stake techniques were honed in his years as curator of Hyde Hall, the RHS garden in Essex, and then RHS Garden Harlow Carr, in Harrogate, and detailed in his book New Gardening, a template for the way we should garden in today's changing climate.
Wilson is designer, plantsman and horticulturist, as well as proof that green fingers are made, not attached, at birth.
"Actually, I wanted to be a rock star," he recalls. "After I left school I had a series of meaningless jobs and played in a band. My Damascene moment came when I helped my dad run a big private garden in Kent as a summer job, realised I loved it and got a last minute place at Hadlow College to study horticulture."
He became a rock star of a different sort, and is set to be a screen star, too, with his own Channel 4 TV series this summer, in which he supervises garden projects up and down the country.
One of his finest landmarks is the Dry Garden at Hyde Hall, in which 260 tons of glacial rocks were hauled in from Aberdeen, along with 800 tons of builders' rubble, to create the ultimate rock garden: a glorious undulating landscape of global plants that have thrived these past eight years without any watering whatsoever.
What makes it more remarkable is that the garden is in a corner of East Anglia where the rainfall is lower than Jerusalem and the wind whips in from the Urals. If plants can make it there, they can make it anywhere — including in heavy London clay soil, which is what Wilson had to contend with at Hyde Hall.
'Small town gardens tend to have everything stuck to the sides'
"The great thing about clay is to manage the surface," says Wilson. “Digging doesn't help because you're just killing everything in the ground, rather than letting the worms do the work for you. If you dig heavy manure into clay, you get adobe walls and mud bricks because you're binding the clay up even more. So the method we use at Harlow Carr, and Rosemoor too, is to manage just the top six to eight inches of clay, digging in a one-inch layer of sharp grit, which helps stabilise the soil so you avoid having concrete in summer and blancmange in winter."
The mistake many of us make is to lovingly prepare a planting hole and leave the surrounding soil. "The unadulterated clay will sit there like a broody demented cousin," says Wilson, "and as soon as it rains, the water will rush into the prepared hole and you'll end up with a sump." In other words, the only way is up, adding layers of grit and lightweight stuff such as composted bark and, as Wilson has done in the Dry Garden, mounding up soil, smallerscale, so that you plant high, improving drainage.
Plants, believes Wilson, should be grown as nature intended. "The ornamental plants we grow in our gardens come from the wild originally. So why do we feed them with fertiliser, pour water all over them and generally give them stuff they don't want or need? They only become soft and sappy, which makes them more prone to pests and diseases.
If you don't water and feed them, you won't need to stake them or tie them in, so you remove half the maintenance." At the core of this is choosing the right plants for the conditions that you have. "Get under the skin of your garden. Sit in a deckchair with a gin and tonic and watch where the sun goes and where it casts shade. When you have got the soil right and you understand your garden's microclimate, then you can research the plants that will grow best and sit back and enjoy them being brilliant."
© GAP Photos/Rob Whitworth
Six plants for London clay soil
Pittosporum: there is an evergreen pittosporum for every size of garden. In summer, they recede into the background; in winter, they make great colour.
Eremurus stenophyllus: makes great vertical statement; at Hyde Hall they grow among roses, looking wonderful. Plant with roots laid out and crown exposed.
Rosa rugosa Roseraie de l'Hay: one of the most trouble-free roses; never gets disease and has beautiful flowers, foliage and fragrance.
Euphorbia: honey-scented Euphorbia mellifera is a beautiful plant and will grow in full sun and semi-shade. It has great architectural quality and subtle leaf colour.
Geranium Rozanne: longest in flower of all the hardy geraniums, from early summer until the first frosts.
Monarda: prairie plants such as monarda, echinacea and rudbeckia thrive on clay if the soil in good shape first.