An urban meadow

It is Chelsea Flower Show time again, one of the UK’s comfortingly traditional events that will always mean that the summer begins with an outpouring of magnificent gardens and floral displays. It is the start of the English social season and, for many, the most prestigious and exciting flower show in the world.

Preparation for Chelsea begin at least one year in advance, when plans are formulated, plants sourced, sponsors organised and applications made by designers to the Royal Horticultural Society for inclusion in the show, which comes together in the grounds of the Royal Hospital in Chelsea, London, between May 24 and 28. There will be 32 show gardens and the Great Pavilion will house over 100 nurseries, with the event filmed and broadcast live by the BBC.

This year the show gardens include the RBC New Wild Garden, sponsored by the Royal Bank of Canada in partnership with the Landscape Agency. It is designed by Dr Nigel Dunnett, who is one of the great plantsman pioneers of our age: he is a reader in urban horticulture at the University of Sheffield and, as director of the Green Roof Centre, well-known as a champion of green roofs and spectacular urban meadows. At Chelsea he is bringing together two important themes from the past 100 years of gardening: the arts and crafts movement and the wild garden.

The linking character in both of these themes is the great 19th-century gardener, William Robinson. An outspoken propagandist for naturalistic gardening, he helped wrench British gardens away from the Victorian ideal of labour-intensive carpet bedding and perfectly raked gravel to appreciate what the wilder side of nature had to offer our gardens.

Dunnett has today extended this idea for the 21st century. “We are updating the wild garden and putting it in an urban context,” he explains. “We are celebrating nature and natural planting but at the same time shying away from being too purist; for example we are combining garden plants with native wildflowers.”

The principle of sourcing local materials (a cornerstone of the arts and crafts movement) is also being updated. Many of Dunnett’s students have been sent to salvage materials from skips and charity shops. “We are building a series of drystone walls using materials ranging from books and old timbers to dinky cars. They will serve a dual purpose as all the nooks and crannies will become bug shelters,” says Dunnett.

These themes appear in what is a fully functioning rain garden. Built-up areas in towns and cities are becoming susceptible to devastating flash floods – in part because so much ground is tarmacked or paved.

In the RBC New Wild Garden, which is designed as a cross between a reservoir and a big sponge, the rain is absorbed and put to work. “The central feature is a reconditioned shipping container that has been turned into an artist’s studio [the art, and furniture, is provided by a young Devon-based artist, Henry Bruce],” says Dunnett. More recycling: “It has travelled over 10,000 miles and we know the names of every port in which it has docked.”

The green roof of the cabin is a landscape in itself with low wet areas and sandy places suitable for nesting bees. It will absorb 50 per cent of the rain that lands, while the remainder will run off into the first of two connecting round pools. These then overflow into borders containing the sorts of plants that don’t mind a drenching (such as Rodgersias and Iris sibirica). The rest of the garden soaks up more water: there are alternating strips of heavy granite paving (“kerbstones salvaged from outside the Natural History museum”) and low planting (Acaena inermis “purpurea”, thymes and fleshy Sempervivum). Overlooking the proceedings is an oak and granite bench, also by Henry Bruce.

All this dovetails nicely with the Royal Bank of Canada’s Blue Water project. This is the bank’s global commitment to help protect the world’s water supplies: it promotes responsible water use through education and, since 2007, has pledged over $28m to 380 concerned organisations. Its Chelsea garden is that grand scheme boiled down to manageable proportions. It is really a matter of common sense, as the idea of a rain-preserving garden should be the norm rather than a Chelsea Flower Show curiosity.

As for the stress and strain of Chelsea – “We always worry about the plants,” Dunnett explained a couple of weeks ago, “especially in this hot weather. We are trying to do things as naturally as possible, so I am reluctant to try and hold things back by artificial means. However, as they are all being grown in Scotland [at Binny Plants nursery, near Edinburgh], I am hoping that they will be kept back anyway.”

The final question about any Chelsea garden is: where will it end up? For many exhibits, this used to be in a skip but the RHS now insists that as much as possible is reused. No problem here: “The whole garden is being reconstructed at the Slimbridge Wildfowl and Wetlands Centre in Gloucestershire.”

There is a strong environmental theme here but the message is more effective for being worn lightly. Dunnett is aware of this: “My last last garden at Chelsea was labelled the Eco Garden. I want to try and avoid that this time and show that you do not have to be weird and wacky to have a garden like this.”

Dunnett’s is a garden that is shaping up to be one of the frontrunners for Best In Show – but the competition is strong. The Australian Garden, by Jim Fogarty for the Royal Botanic Gardens Melbourne, symbolises a monumental journey from the outback to the urbanised coast with a vivid planting palette of bright colours. Ann-Marie Powell is working with Sir Peter Blake to create the British Heart Foundation Garden, and B&Q has already hit the headlines with garden designers Laurie Chetwood and Patrick Collins’ “vertical grow box” which promises to dominate Main Avenue. Finally, the Principality of Monaco makes its debut at the show with designer Sarah Eberle’s take on high-density sustainability.

Chelsea Flower Show, Tickets for this year’s Chelsea have sold out but Hampton Court Palace Flower Show tickets are now on sale.

Royal Bank of Canada Blue Water Project

The Landscape Agency

Henry Bruce

Binny Plants

How to cultivate a shipping container

Dr Nigel Dunnett is in demand at the Green Roof Centre in Sheffield, writes Nathan Brooker. His enterprising approach has found him not only designing the Royal Bank of Canada’s garden at this year’s Chelsea Flower Show, but also landed him the role – along with co-designer James Hitchmough – as a lead horticultural design consultant for the London 2012 Olympic Park.

A pioneer of what has become known as the “Sheffield school of horticulture”, Dunnett creates highly visual gardens – predominantly in urban settings – that stress ecology and biodiversity, while still being low-maintenance enough to be shrewdly cost-effective.

The school is famous for its innovative approach to green roofs. Usually cultivating areas of planted vegetation on the top of houses or offices, green roof technology is being used in this year’s RBC garden to transform an old shipping container. Dunnett talks through the research that led to the shipping container’s colourful new haircut:

“To make a fantastically beautiful, flowering meadow on the top of a roof, you need to use very modern, lightweight materials for the growing medium and soil. So we don’t use soil at all. We use crushed brick or expanded clay granules, which are like the honeycomb inside Maltesers: they weigh nothing but they soak up water.” Mixing these in with small amounts of compost, it is possible to create deep layers of soil or substrate without much weight.

The next stage is to carry out 500 species trials. With its huge area of mini-test sites, Sheffield’s Green Roof Centre is moving away from the sedum species that have characterised first-generation green-roof planting. Future green roofs promise to be more varied and lovely than ever.

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