“I am a woodlander; I have sap in my veins,” Roger Deakin writes here. The late author, an admired nature writer and broadcaster, is on a mission to get to the heart of something huge and elemental – to understand not just trees, but the very essence of wood.

Deakin’s approach is to start from home and work outwards. We begin at his old Suffolk farmhouse, with its ramshackle shelters, home-made furniture and esoteric wooden ornaments. He reminisces about his youth, his inspirational prep-school biology teacher, the field trips in the New Forest and his classmates, some of whom have been similarly inspired to make a life studying nature. He heads off to Europe, Australia and Central Asia in search of trees, naturalists and aborigines. But this is not so much a book about trees as a lament for his lost youth and a gentler world populated by craftsmen and country traditions, in contrast to today’s cloned, suburban reality.

I have looked forward to Wildwood more than any other book that I can remember. Deakin’s previous one, Waterlog (1999), a record of his swims in the waterholes of Britain, was one of the most evocative, moving and original books written about this country. Its discussion of nature, modernity, swimming, countryside access, literature and local identity combined in a narrative whose quietly reflective tone slowly took one over.

When I got back from holiday last summer to hear that he had died I experienced a strange sense of loss. I had never met Deakin, but I felt I had lost a friend and mentor. He died four months after being diagnosed with a brain tumour, at the age of 63.

Wildwood is his attempt to do for trees what he did for water. The tone is different, however – self-indulgent, overbearing, pretentious even. He has always championed the smallness of things, but the section on his house is so insular it can read like one of those Christmas circulars. Do we need to hear about the lepidopterists and their beloved moths, or his pencil obsession, in such detail? Where his house and moat seemed charming in Waterlog, one tires of his domestic arrangements in Wildwood.

When he finally takes off to revisit the places that first inspired him as a boy, the book picks up. We visit the New Forest. We learn about the language of rooks, about how walnut veneer reaches the dashboard of a Jaguar, the process by which willow is made into cricket bats, and about the treehouse community of Tinker’s Bubble in Somerset.

There are details to savour, such as the fact that the Australians must come baggy green cap in hand for our willow to make their best bats. When Deakin repeats to his old schoolfriend George Peterken the common assertion that climate change will require us to start importing trees from Eastern Europe, the naturalist is dismissive: “George considered the whole notion complete nonsense. It ignored, he thought, the resilience of our trees and the past fluctuations in our climate they have successfully withstood.”

The story moves abroad. Some of this is illuminating but much, particularly the Australian section and his journeys across Kazakhstan and Kyrgyzstan in search of apple and walnut, reads like a long list of meetings, journeys and goodbyes. Editing seems to have been forgotten. Characters we’ve met are introduced again, amid huge thickets of pointless detail. Perhaps because this book was published posthumously, its editors couldn’t bring themselves to prune the text.

There are, nevertheless, wonderful passages, such as his evocation of the Bieszczady Woods in Poland, scarred by German, Ukrainian and Soviet atrocities and later by the Communist government, who forcibly moved its mountain people to other areas. But by the end, one wonders what it all means, and why it needed to be such hard work.

Wildwood, then, is for the committed naturalist – someone whose eyes light up at sentences like this: “When we reached First Bog, we lay flat on the wooden bridge and searched the peaty water for the aquatic lesser bladderwort, another of the local insectivorous plants.”

I prefer to remember Roger Deakin for Waterlog, where in a rare moment of introspection he wrote: “I am just an ordinary man-in-the-pool swimmer of no more than average ability, quite happy as long as I am afloat somewhere interesting and preferably beautiful.”