Sandy’s Garden ... horse chestnut trees

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Ipppocastano, the Italians call it. Aesculus hippocastanum is the plant’s pukka name – and that illustrates the value of the system of internationally recognised botanical names for plants.

It came by its common name from the mistaken belief that the tree was a kind of chestnut, similar to the sweet chestnut which we use in stuffing at Christmas, together with the observation that eating them cured horses of chest complaints.

In fact, the nuts are slightly poisonous; and they don’t cure horses of chest complaints either.

And, as you have no doubt guessed already, we usually call it the horse chestnut tree.

So what family of trees does the horse chestnut belong to if it is not, in fact, a proper member of the genus Castanea, the chestnut family?

Well, Linnaeus called it Aesculus hippocastanum – Aesculus after the Roman name for an edible acorn because of the mistaken belief that the nuts could be eaten – and hippocastanum like the nuts from the very similar-looking Castanea (the edible chestnut tree), compounding the name with the Greek name for a horse – ‘hippos’ – to come up with Aesculus hippocastanum.

But, in fairness, Linnaeus recognised that, though it was like a chestnut tree, it was not actually a chestnut tree, which is why he called it Aesculus hippocastanum.

The genus Aesculus contains something in the order of 20 species of trees – some deciduous and some evergreen – that are native to the temperate areas of the northern hemisphere.

Nowadays they are regarded as being closely related to maples and dipteronia, and don’t worry if you have never heard of that latter tree, for there are only two species and they are pretty much confined to China.

But maples and horse chestnuts are widely grown in the United Kingdom nowadays, the horse chestnut, in particular, having become a favourite tree for planting in municipal parks since its introduction to these islands in the late 16th century.

The landscape designers include the trees for their attractive foliage, their statuesque size and their general appearance of grandeur and municipal reliability.

Children, on the other hand, regard them as a wonderful source of conkers.

In years gone by, the chestnuts have been put to a wide variety of uses. They were used in France and Switzerland in the manufacture of a sort of bleach for removing spots from linen and woollen cloth without damaging the fabric in any way. And, as I learned from the Internet, “During the two world wars, horse chestnuts were used as a source of starch which in turn could be used via the Clostridium acetobutylicum fermentation method devised by Chaim Weizmann to produce acetone. This acetone was then used as a solvent which aided in the process of ballistite extrusion into cordite, which was then used in military armaments.” Yes, having read that a couple of times, I think I know what it means!

Horse chestnut trees even had a use in the brewing trade in previous centuries. In Bavaria, the trees are still very common in beer gardens where they were originally planted for their leaves – not for their decorative properties but because the deep shade generated by the dense foliage kept the ice cut from rivers and lakes in winter cool well into the summer months.

And even yet, so I am told, the trees’ shade is welcomed on hot summer days by customers quaffing a pint or two of the local beer.

Yet the very qualities that make the trees popular in parks and beer gardens make horse chestnut trees unsuitable for the average town garden, where their height would be overpowering, their shade excessive and their spreading root systems a menace to the foundations of the gardener’s home.

Sandy Simpson, Polmont Horticultural Society