Dear Readers, the brown and distorted leaves of the horse chestnuts on Hampstead Heath tell their own story of how things have changed during my lifetime, and particularly during the last twenty years. If you had a look at the short film in the blog that I did a few days ago, you’ll have seen that loveliest of things, a horse chestnut in full leaf. These days, we’re lucky if they get past flowering before the leaf miners and the various fungi that attack the tree have turned those big palmate leaves into a patchwork of brown and yellow, before they shrivel and fall.

Horse chestnut leaves, July 2022

It’s said that these various ‘pests’ won’t kill the trees, but I do wonder if the leaf damage over successive years weakens them. After all, most of them are relatively recent. The leaf miner, a tiny moth whose caterpillars actually live between the layers of the leaf, was only sighted for the first time in 2002. Since then it has been working its way steadily across the country, until most of our horse chestnuts are a tatty mess long before they should be losing their leaves. The trees are also producing fewer and smaller conkers, which is a shame for any remaining children who like to play with them. However, there is evidence that blue tits are starting to get the hang of feeding on the larvae, and it’s hoped that parasitic wasps might recognise this handy food source, as they often do. Let’s hope it’s soon.

In ‘Nature’s Calendar’, Rowan Jaines tells the story of how the horse chestnut first arrived in the UK. It’s been here long enough for many people to think that it’s a native, and to be honest I thought it was another one of the things that the Romans had done for us, but no. The first record of the Horse Chestnut in Europe is from 1576, when the tree was planted in the gardens of the imperial palace in Vienna. It was so impressive that it spread across the gardens of the continent, with two trees arriving in France in 1615. One of the trees lived in the grounds of the Hotel Soubise in Paris until its death in 1840, while a second lasted until 1767 in the Jardin des Plantes. Louis XIV loved the tree so much that he ordered avenues of the trees to be planted at Versailles, assuring that the tree would be fashionable, and would spread across the estates and gardens of the rich throughout the eighteenth century.

However, its place of origin was something of a mystery. The first trees planted came from Turkey, and horse chestnuts were thought to be of Asian origin right up until the nineteenth century, when it was found that their home range was actually in the Balkans, in the mountains of Bulgaria, Albania and Greece.

Horse chestnut bud

However, what’s very interesting to me is how the tree got the name ‘horse chestnut’. I always wondered if it was something to do with the shape of the bud, which could possibly look like a horse’s hoof (if you squint). However, it appears that the conkers were ground up and used as medicine for coughs and chest complaints in horses as far back as the sixteenth century. In fact, chemical compounds in conkers have been found to control inflammation and swelling and reduce the accumulation of the fluid that causes the horses to cough, so there is scientific evidence for centuries-old practices. I always find it heartening when the skills of generations stand up to twenty-first century scrutiny, as many often do. Let’s celebrate the horse chestnut, that most impressive of trees, and let’s hope that nature soon finds a way to balance the effect of its parasites.

Horse chestnut flowers