“A culture,” WH Auden wrote, “is no better than its woods.” A place without trees, he implied, has no roots, no strength and no shelter. Taking that line as his point of departure, Roger Deakin decided to go in search of what he calls “the subconscious of the landscape”: our trees, woods and forests. “They,” he writes, “have become the guardians of our dreams of greenwood liberty, of our wildwood, feral, childhood selves . . . they hold the merriness of Merry England, of yew longbows, of Robin Hood . . . they are also repositories of the ancient stories.”

The result is a breathtaking book. Much of it is about Britain: Deakin studies the portraits of various Green Men in Devon, searches for evidence of wood henges on Salisbury plain and traces the route from walnut trees to Jaguar dashboards, from willow woods to cricket pitches. But Wildwood is also far-reaching. In search of walnuts, he travels to Kyrgyzstan, home to the world’s densest walnut forests. Intrigued by the origins of the old-fashioned English apple, he journeys to its probable place of origin in – don’t get confused – Kazakhstan. He goes wherever there are interesting woods and interesting people, be it north Wales or the Australian outback.

Deakin, it becomes clear, is very much a child of the 1960s. He compares peasants in Asia to “the women you used to see on the covers of . . . Incredible String Band albums”. He sort of falls in love with a peasant girl, partly because he likes “the hippieish sloppy Joe pullovers she always wore”. He’s a man who prefers wax to wires, approvingly quoting Thoreau: “Electricity kills darkness, candlelight illuminates it.” But there is nothing fanciful about the book. Deakin comes across as a rugged survivor, a man who gets lost in forests, sleeps rough and forages for food and seeds. He prefers sleeping outdoors, he explains, because “the house represents what we ourselves would like to be on earth: permanent, rooted, here for eternity. But a camp represents the true reality of things: we’re just passing through”.

As a botanist, conservationist and carpenter, Deakin frequently drops in wisdom about wood. Sycamore is best for milk pails because it imparts no taste. Salix alba coerulia is the best willow for a bat. He describes techniques for grafting and pollarding, for hedge-laying and coppicing. Frequently, he drops intriguing nuggets into the narrative, such as the fact that “the celtic prefix af or av also signifies ‘apple’ as in Avalon or Avignon”.

He has a great ear for the bird-song he hears from his bothies and bivouacs: he mentions a “glissando” of chaffinches, the “cool oboe notes” of owls. There is a fair amount of botany, but it’s vividly written. When he takes his foot off the brakes, the effect can be hypnotic: “Blackbirds arrowed silently through the shadows. Mist swam into the deep green of my glade through the waving seaweed of nettles, goose-grass, pink campion, bluebells, grasses and ferns.” One moth, he writes, “looks like a teddy bear with a handlebar moustache”.

Deakin’s previous book, Water-log, was an account of an eccentric journey swimming through the canals and rivers of Britain. Wildwood is vaguely similar. Again, you see the world from an unlikely viewpoint; not, this time, from the surface of the water, but from inside the chaotic, uncleared spaces left in our landscape. The vibrancy, noise and resilience of nature suddenly become clear; as, inevitably, does its fragility: “It is salutary,” he says, having inadvertently exposed a nest, “to be reminded of the extent of your own power and our potential for accidental brutality.”

Deakin clearly has timber deep within his psyche: he rebuilt his Suffolk cottage by hand, restoring 323 beams. He reads and re-reads Hardy’s The Woodlanders. He sees trees as living beings and describes their “stroppiness”, “anger”, “defiance” and “muscularity”. He clearly shares some of those attributes because he occasionally writes – through gritted teeth – about the stupidity and unsustainability of modern life. “The enemies of woods are always the enemies of culture and humanity.”

Reading Wildwood is an elegaic experience, not because of environmentalist doom-mongering (the book is much more a celebration than a lament), but because Deakin died last summer, at the age of 63. When books are published posthumously you almost hope they’re not this good, because then you might feel the loss less acutely.

Wildwood: A Journey Through Trees by Roger Deakin

H Hamilton £20 pp391

Available at the Sunday Times Books First price of £18 (inc p&p) on 0870 165 8585

Times Recommends

• Sarah Palin and the Palindromes: 7 extraordinary connections
• Physics for Future Presidents: The Podcasts
• 10 Books Not To Read Before You Die