Flower smellers have sex on the brain

Another Life: The whins that gild the west, never more spectacularly brazen than this spring, delivered billows of a fragrance widely agreed to be "coconut", even by people who don't eat biscuits, thank you. Now it's the hawthorn, wafting from the hedges in startling little gusts of warmth that smell of - what? Sex, according to the English, who are, of course, obsessed.

Geoffrey Grigson began it in his Englishman's Flora, now half a century old: "The stale, sweet smell from the triethylamine the flowers contain makes them suggestive of sex." Richard Mabey's recent Flora Britannica, got even more explicit: "Triethylamine's fishy scent is also the smell of sex - something rarely acknowledged in folklore."

Even Charles Nelson, adopted son of Irish botany, has written of "that heavy, musky fragrance with sexual undertones". I must have missed out on one of nature's promptings - surprisingly, perhaps, since the scent of flowers has been among my keenest joys. A tower of old-fashioned sweet peas intoxicated the polytunnel through most of last summer. And this spring, planting Brompton stocks in a patio fishbox, I was celebrating a potent memory from childhood: climbing the chalk cliffs east of Brighton to pick the hoary stocks - "garden escapes" as botanists would insist - flourishing in clumps along the ledges. Their rich, clove-scented aura, potent even in a sea breeze, rises now above the purple plastic of the Galway and Aran Fishermen's Co-operative: No Unauthorised Use.

You should also stand enraptured downwind from my white shrub roses - Blanc Double de Coubières, a conceit born years ago from falling for the Jean Cocteau film, La Belle et la Bête. It was in black-and-white, but I could smell the roses.

All this makes me a natural for aromatherapy and essential oils.

Geranium, suffusing my workroom, can inspire a foolish equability even on the gloomiest winter day. There is much New Age fantasy written about the "healing modalities" of flowers, but that their scents can engender such widespread human uplift is, at the least, a fascinating coincidence.

Richard Dawkins is right to debunk any idea that flowers were put into the world for the benefit of people, and to reproach even ecologists tempted "to see all of life as a sort of mutual-support encounter-group".

Flowers, with scents and colours so attractive to pollinating insects, are, as he says, "for spreading copies of instructions for making more flowers". But however selfish their genes, they seem to be capable of involving their human neighbours in fairly far-reaching ways.

The molecules of flower perfume evaporating into the air reach 347 different sensory receptors in the nose, and the olfactory nerves send messages directly to the limbic system of our brains, dealing with instinctive emotions such as memory, aggression - and yes, sex.

The natural fragrance of flowers and trees can be analysed into its chemicals - benzines, monoterpines and the rest - and copied synthetically for Chanel No 5 or the sickening confections of "air fresheners". Who knows what impulses have been built into the corporate pheromones that now pervade our supermarket aisles?

In nature, flower scents and essential oils are part of the love-hate relationship with insects that has been evolving since the Cretaceous.

Many of the oils that give plants flavour - the mustard oils of the cabbage family, for example - were brought about by natural selection as defence against insect damage (not that this has always helped, since some insects - such as the cabbage white butterfly - have proceeded to get hooked on oils of a particular type).

The scents, on the other hand, like flower colours and ultra-violet petal patterns, which are guides to hidden nectar, are aimed at attracting insects for the distribution of pollen; not only bees, but butterflies, night-flying moths, wasps, beetles and many kinds of fly. For most, the sense of smell is located chiefly in the antennae. And while honey bees, for example, may show obsessive preferences in their choice of flower - heather, clover, apple blossom while it lasts - one experiment showed bees able to distinguish between 44 ethereal oils.

Some of nature's floral scents, meant to simulate various kind of decay, and attracting blowflies and other waste disposal insects, actively disgust the human brain. But enough thrilling fragrances remain (lilac, jasmine, honeysuckle, lily-of-the-valley, wallflowers) to stop us in our tracks, neurons buzzing with delight, to wonder on the human function of such magic.

Could it be to make us want to plant gardens, for the spreading of copies of instructions for making more flowers?