Nature Studies by Michael McCarthy: The chestnut that conquered the world

It is curious that the horse chestnut tree, whose nuts are useful only to small boys playing conkers, is so much better known in Britain than the sweet chestnut, whose nuts have supported whole societies.

I have the general impression that most people would recognise a horse chestnut but would pass a sweet chestnut by. Perhaps that's understandable, as horse chestnuts, introduced into Britain only about 400 years ago, have now been planted all over the place as ornamental trees, and magnificent ornaments they are, come late April or early May, lofty and majestic and lit up by their foot-high creamy white blossoms, their "Roman candles". They're one of the events of the spring.

Sweet chestnuts flower later and less dramatically, and they're not really public show trees, of parks and playing fields and avenues, in the way horse chestnuts are; they're trees of the woodland, blending in. They're quite unrelated to horse chestnuts, being members of the extended beech family, while conker trees are in a family of their own. But they're not wholly dissimilar; the quick way of telling the difference is that the big long leaves of the horse chestnut are rounded at the ends, while those of the sweet chestnut are pointed.

The Romans are thought to have brought the latter to Britain, as food for the legions. What, you exclaim, the guys who beat Boudicca and built a wall from sea to sea did so on a diet of nuts? But they weren't eating the nuts. They were eating chestnut flour, baked into bread.

Call me naïve, but I still remember how surprised I was when I first learnt that flour, the basis for the stuff of life, did not have to come from wheat, or indeed from any cereals. It was in the South of France, a long time ago, on holiday at the far western end of the Côte d'Azur, near the seaside town of Le Lavandou. When you get this far west, the commercial strip of the Riviera is finally petering out and the natural world is starting to show itself, so there is more to interest you than just the beaches and the bouillabaisse restaurants where they want 40 quid for a bowl of soup. One day we ventured inland to the pretty hilltop village of Bormes-les-Mimosas, and I remember thinking, what if we keep going? What if we just keep heading north? What's up there?

What was up there was a vast sweet chestnut forest, covering the hills of the Massif des Maures, and we drove through the undulating glossy dark green landscape for mile after mile, having left other tourists behind, until we came to the little town of Collobrières. And this, it turned out, is the chestnut capital of the world.

I learned to my astonishment that this was the centre of a region which for hundreds of years, because of its hilly topography which made the cultivation of cereals impossible, offered no basic sustenance other than chestnuts to its people; yet they survived perfectly well. Their staple was bread baked out of chestnut flour, tasty and nourishing, but they made all sorts of other things, from polenta (although it's made from maize flour now, chestnut flour was its original base) to marrons glacés, the candied chestnuts we sometimes encounter at Christmas, and chestnut ice cream, chestnut purée, chestnut syrup, chestnut liqueur. In October in Collobrières, they have a chestnut festival.

In fact, in many parts of southern Europe, from France through Italy to Greece and across to Turkey, sweet chestnuts have historically played a huge role in the local diet and the local economy, and still do, as a storable carbohydrate; whereas we encounter them merely as a mildly exotic, warming treat in autumn and winter, roasted on a brazier in the street (usually by some snuffling geezer with fingerless gloves and a cold).

But we rarely gather the nuts ourselves, and perhaps that's the reason why we in Britain are not familiar with the tree. My own experience is that British sweet chestnuts are disappointing, from a gastronomic point of view: when you open the spiny outside, the nut is usually split in to two or three small fiddly pieces and is not the big, fat munchible dollop you were hoping for. The plump round chestnuts we see about now in the shops or roasting on braziers are imported, mainly from Italy.

I would guess that this is a matter of selective breeding by the chestnut-conscious societies of southern Europe. Indeed, one of the things I learned from Collobrières was the difference between a châtaigne, which is the generic French word for any sweet chestnut, and a marron; the marron is the round, undivided nut which is found in greater or lesser numbers according to the individual tree.

The end result, anyway, is that in Britain we go in ignorance of our sweet chestnut trees, yet they are lovely things, and even if not showy blossomers in our streets, they have their own magnificence, being able to grow to quite an enormous size, especially in their girth. This autumn the Woodland Trust is asking people to record more examples of sweet chestnuts as part of its Ancient Tree Hunt. They can live for thousands of years: the giant Tortworth Chestnut in Gloucestershire, for example, was already a landmark in the reign of King John.

So expand your horizons from horse chestnuts, that's my advice. Remember, with a handful of conkers all you can do is take on the spotty kid next door; but with a bowlful of sweet chestnuts under your belt, you can take on Boudicca herself.

m.mccarthy@independent.co.uk