Common horse chestnut

Horse chestnut trees: facts and stories

Named after the seeds that look very similar to edible chestnuts, horse chestnut trees are often confused with sweet chestnut trees, and vice versa. So, how do you tell them apart?

At first glance, the seeds of sweet chestnuts and horse chestnuts do look alike. They both have a whole or half ball shape, and a smooth, dark brown, glossy shell. Each of the seeds from both trees also has a light brown, matte patch.

Differences can be seen in the sweet chestnut seeds though, which have a pointed top with a small tuft of hairs. Sweet chestnut seeds are enclosed in a green-yellow outer case (burr) that is covered with tightly packed spines, making the whole thing look a little like a hedgehog. These spines serve as protection for the sweet chestnuts inside: the very same delicious treats that you see being grilled around the city streets or served in sweet shops as candied chestnuts.

Horse chestnut seeds are more rounded, and their burrs have fatter, shorter spines that are more widely spaced out. These seeds cause sickness when ingested by humans, and are slightly poisonous. The Latin name for this tree, Aesculus hippocastanum, translates to ‘chestnut oak for horses’.

Did you know?

The magnificent flowers on horse chestnut trees don’t just attract bees: they also have a seductive appeal for humans too. Some scientists hypothesise that plants have the ability to manipulate humans. Their beauty, colours, scents and tastes could all be strategies for them to boost pollination, reproduction and ultimately spreading out across the landscape.

The beauty of these trees has helped them to travel great distances and become naturalised all over Europe. In French, horse chestnut trees are called marronnier d’Inde (‘chestnut of India’), but their native habitat is actually the Balkans and south-eastern Europe. For thousands of years, the trees grew in the wild in the mountain forests of Albania and northern Greece.

Then, in the 16th century, horse chestnut trees started to be planted in the imperial gardens in Vienna. The tree was spread to botanical gardens, regal parks and eventually the grounds of chatelaine houses. Two centuries later, horse chestnut trees had conquered all the cities in Western Europe. These trees acclimatised so well that they are almost thought of as a native species. They represent city trees in all their glory. Horse chestnuts were one of the favourites of Leopold II of Belgium, who liked them being planted along the grand avenues in Brussels.

The benefits of horse chestnut trees

Horse chestnuts are the largest flowering trees. They often have a majestic appearance, and their beauty has made them very popular for planting in towns and cities. They are one of the most commonly planted species* for decoration in urban avenues, parks and playgrounds.

However, the benefits of this tree aren’t purely decorative. The extensive, very dense foliage is great at producing oxygen, and also helping to purify the air that we breathe. Horse chestnuts are one of the best trees when it comes to fighting air pollution and capturing CO2 (which is stored in their wood). The leaves filter fine particles from the air too. Lastly, the shade that these trees cast is ample and very dark, which has a cooling effect on the surrounding air. This is particularly beneficial during heatwaves!

The fruit of horse chestnut trees isn’t edible, but it has numerous uses (see above) and recognised medicinal properties. Extracts from the tree are used for treating problems with blood vessels.

How to recognise a horse chestnut tree

Leaves

large, fan-shaped, with compound composition of 5–7 mini leaflets (folioles)

Folioles

long and oval-shaped, with coarsely serrated edges

Foliage

bright, dark green in spring/summer; red in autumn; and no foliage in winter

Flowers

white with yellow and pink patches; grouped in large, erect clusters (panicles)

Fruit

burrs; round, green, spiky capsules (~6cm)

Seeds

brown to reddish brown, smooth and glossy

Bark

reddish brown, becoming blackish grey; scales that flake off in patches (desquamate)

Specifics about this tree

This tree is firmly anchored in the ground with its large base. However, it does not seem to be that still at all. From the base, its trunk winds around on its axis, with three winding main branches. It looks to be very much alive. Its animated spiral structure is a nice image for the backdrop of funeral precessions, with the spiral evoking the circle of life and rebirth. Uniting nature and the universe, the tree represents a breath of life.

All the horse chestnut trees here have the same shape and semblance of movement. In the winter months, they form a guard of honour at the cemetery’s entrance. In spring, their foliage sags under the weight of the flowers, and the paving below transforms into a carpet of white petals. Then, in the summer, the trees’ leaves create a huge vault of green that invites visitors to look up to the heavens.

All across Europe, horse chestnut trees are affected by a disease, and these specimens here haven’t managed to evade it. On the right, you can see one tree that has lost all its branches, leaving just its trunk. It has been left in place as a shelter and source of food for insects, birds, moss and various types of fungus. To its left, a sapling has been replanted to take the place of the dying tree. This band of trees illustrates the cycle of life and death.

(Story and photos created by Priscille Cazin- Sylvolutions)

This portrait is:

- Enriched with an illustration from the Belgian Federal State Collection on permanent loan to the Meise Botanical Garden.

- An initiative of Christos Doulkeridis, Mayor of Ixelles , Audrey Lhoest, portfolio holder for Environment, Green Spaces and Planting, and Tourism and the Ixelles Communal executive