Canada on canvas opens up a new world

The Canadian landscape in all its bleak beauty is the subject of a riveting show celebrating the country's pioneering Group of Seven

Tom Thomson and the Group of Seven are such iconic figures in Canadian art that one hesitates to admit just how ignorant one is of their work.

They were the painters who not only defined the view of Canadians of their landscape but also of themselves, and yet they are hardly known over here. Indeed, the Dulwich Gallery exhibition is the first major show of the group in Britain since they first appeared in London during their heyday in 1924.

"Do you think that the British will like it," a Canadian broadcaster asked me on the way out, adding a little tentatively, "and how will they judge it?" They needn't have worried. Thomson and the Group of Seven astonished – and shocked – the Canadian art establishment when they first started exhibiting and they still have the capacity to excite and surprise us now.

Right in the first room you are faced by two of the most totemic and radical images of their new way of depicting landscape: Tom Thomson's Jack Pine and The West Wind from 1916, are set against the water and hills of Algonquin Park, the brash and windy wilderness he made his own. Gone are the naturalistic landscapes after the US Hudson School, then the dominant influence north of the border. In comes all the confidence of commercial art imagery, thick post-impressionist brush strokes, the bright colour of the expressionists and the cut-off compositions of Japanese prints.

Perhaps it's as well most of us don't know as much as we should about this movement because one of its excitements is the sense you have as you go through it of a group of artists lapping up and converting into their own terms all the novelty and inventiveness of the art blowing in from Europe. That is not – despite Canadian fears – to deprive the group of its national individuality. It was true, after all, of British, Italian and, indeed, Japanese art of the time. What made Canadian art so special was both the particular cold and windswept landscape of the country and the adverse conditions in which these painters had to go out and try and capture it. If you wanted to work out there en plein air, you had to do it quickly and roughly. The wind and cold didn't allow hesitation or deviation.

Tom Thomson inevitably leads the show. Tall, handsome, a skilled canoeist and angler, and hopelessly attractive to women, he had the incomparable attraction of dying young and in mysterious circumstances. After three years of camping out and sketching in Algonquin Park, returning each winter to Toronto to paint up the finished pictures in his studio, his upturned canoe was found drifting on a lake, his body turning up some nine days later. Suicide, murder or accident? Legions of books have been written proposing every alternative.

In those three years, however, he had pioneered a new style and given it the form of direct encounter with nature which profoundly influenced fellow artists in the decade after his death in 1917. His finished works are monumental enough, but it is his oil sketches that are, in many ways, his greatest contribution to art. Done quickly on small boards, the weather and temperature restricted his pallet to a few colours and his brush to bold and heavy strokes. Sunset and sunrise, along with night, barren rocks, rippled water and windbent pines, were the preferred themes for Thomson and his colleagues. Dulwich has gathered the sketches into a single room and they are totally compulsive.

Thomson, mourned by his fellow artists, died well before the actual foundation of the Group of Seven in 1920. A group founded as much for exhibition purposes as intimacy, they showed for over a decade into the Thirties. Like Thomson they based their work on trips into the wilderness. The Dulwich exhibition takes them geographically, as they spread to the north and west to the Pacific coast, the Rockies and finally the Arctic itself. All were intent on finding a new and distinct way of picturing Canada's landscape and inevitably it is their views of the forests, mountains and lakes which have made them special to the Canadians.

But to anyone coming new to this movement, it is their development of individual styles that fascinates. Six of the group worked for the design company, Grip Ltd of Toronto, and it shows. Decorative approaches from art nouveau to art deco make their appearance as do the motifs and compositions of 'japonisme'. A.Y. Jackson was the most physically adventurous, Franklin Carmichael the youngest. Arthur Lismer and Frederick Varley both came from England, where they'd studied painting. J.E.H. MacDonald had come to Canada from Durham at the age of 14 and again trained as an artist, developing a more visionary view of landscape. Jackson, Lismer and Varley all worked as war artists in the First World War and that too shows in some of their works on their return.

But, if Thomson dominates the beginning of this show, it is Lawren Harris who closes it. To some he was the finest artist of them all. Certainly the richest. The scion of a wealthy industrial family he had the early advantage of being able to provide his friends with his own box-car for trips to the wilds, which was towed behind a train, released at an appropriate spot and then picked up again days or weeks later

He'd studied in Germany and, from early on, was a major energiser of the group. An early oil sketch from 1914 of Winter shows his powerful sense of image and muscular composition. It was a gift he developed in a more and more mystical way as he moved north to the increasingly barren landscapes of Lake Superior and the Arctic. Embracing the then fashionable beliefs of theosophy, with its symbolism from the East, his landscapes became less and less about texture and more and more about nature as an ideal until, finally, his paintings become stark symbols of eternity as seen in his depictions of mountains and icebergs. As near to early Disney cartoons as to modernist landscape, they may not be always the greatest works of art but they are certainly the most powerful of images.

This exhibition, the product very much of the individual enthusiasm of the curator, Ian Dejardin, has done Canada proud and the British gallery goer a service.

Painting Canada: Tom Thomson and the Group of Seven, Dulwich Picture Gallery, London SE21 (020 8693 5254) to 8 January 2012