Who would want to read a whole book about a teenage boy’s gap year? When most 18-year-olds take time off before university, they either head for Thailand to experience middle-class Western culture in warmer climes with more drugs, or spend six months shelf-stacking and six months ‘finding themselves’ at a Ugandan orphanage. A tedious evening in the pub during freshers’ week when all the gap year students bore one another into submission about how much better Mexico made them is normally enough. Leif Bersweden thought so much of his year off, though, that he wrote 360 pages about it.

But the difference between most gap years and the one that Bersweden describes in The Orchid Hunter: A Young Botanist’s Search for Happiness is that this teenager wasn’t trying to find himself but all 52 species of native orchid that flower in the British Isles. Most staid grown-ups are unaware there are so many orchids popping up in woodlands and sand dunes all around them, let alone teenagers whose definition of a ‘wild’ afternoon normally involves a muddy field at a music festival, not hunting through soggy peat for a pale green flowering spike of Hammarbya paludosa, the bog orchid. But Bersweden has been obsessed with orchids ever since, aged seven, he came across a ‘flower that looks just like a bee’.

That bee orchid, Ophrys apifera, has a sex life far beyond the dreams of most teenage boys. The Orchid Hunter reveals the naughtiness of many orchids in tricking insects into thinking their flowers are in fact alluring females, often before the female insects have actually hatched. A randy bee comes across something that looks, smells and even feels like a lovely lady, and so he goes for it:

Excited by this, he alights and attempts to mate with the ‘female’, often vigorously and for prolonged periods. During these fruitless exertions, the bee knocks into the column— the reproductive structure consisting of both male and female parts — which drops two tiny, sticky pollen sacs on to the bee’s back. Eventually, he gets frustrated by the lack of action and buzzes off in search of a more enthusiastic partner.

Bersweden finds the bee orchid’s relatives, the fly and the early spider orchid, both of which also rely on horny insects for their own sex lives to work.

As a coming-of-age book, this has all the sex you’d expect: it’s just that it’s between the often tiny plants that Bersweden is hunting. Things get particularly fruity when he encounters the slightly disturbing hybrid of the monkey and lady orchids, which he says ‘simply can’t keep their hands off one another’. He frustrates his parents with an act of rebellion, sneaking out of the house without permission one evening and receiving a furious volley of text messages from his father when his absence is discovered. His father isn’t angry because he suspects the teenager is fumbling about in a bus stop with a girlfriend. One of his messages reads: ‘You’d better not be orchid hunting.’ And of course he is looking for the burnt orchid.

His road trip is amusing and fraught with the sort of difficulty you might expect in a low-rent film involving teenagers driving long distances — his car breaks down; he spends days agonising over whether a ‘Sharon’ who directs him to one particularly elusive specimen in Ireland is a man or a woman — but it is also melancholy. Bersweden has spent his adolescence far better than the rest of us. He has clambered over the limestone pavements and chalk grasslands of our extraordinary countryside, and read extensively about botanists from the 17th century who first discovered many of these strange and wonderful plants. But he, like the covert teenage botanist that I was, seems to see it as a misspent youth that he needs to apologise for, hiding his gap year plans from his friends, and wondering if he will ever find someone who loves the thrill of chasing the lady’s slipper orchid as much as he does.

Yet the satisfaction of finding plants which drove the Victorians so mad that they hunted many of them to the brink of extinction seems so much richer than anything a conventional ‘cool’ gap year could offer. Bersweden gets so caught up in the joy of finding orchids that his very lovely writing occasionally goes a bit over the top, describing a breakfast before finding the loose-flowered orchid as ‘heaven-sent scrambled egg’.

Sure, it might be a while yet before orchidelirium becomes a gap year phenomenon. But Bersweden’s greatest achievement in writing about his gap year is persuading readers that it’s us, not the boy who spent a year looking at flowers, who need to get a life.