Horse Chestnut

All photos taken by the author. Last updated April 23, 2021.

This tree has been severely pruned to keep it from touching power lines. On November 19 it still had many leaves attached and lots of fruit on the ground underneath.

These deciduous non-native trees produce hard fruit protected by a prickly outer surface. These fruit, known as conkers, cannot be eaten by humans but are consumed by many animals. I recently drilled holes in more than 100 horse chestnuts for a friend’s kindergarten class to make mobiles out of and when they went to check on them they had all been eaten by animals. If this sounds like something you want to do, I can say from experience that it is much easier to drill through fresh ones (soft like an almond) than aged ones (like hardwood). Horse chestnut trees have palmately compound leaves of 5-9 leaflets per stalk and the stalks are attached opposite to each other on the tree’s twigs.

Palmately compound leaf with 6 leaflets. Green in the spring and summer, horse chestnut leaves turn yellow, orange, and brown in the fall.
A conker in the grass.
The prickly outer casing of a horse chestnut. The cases fall off the fruit when dry, three prickly pieces per dry fruit.
Vertical twigs on a horse chestnut branch. Notice the opposite attachment of leaf stalks in the lower left corner of the photo. You can also see the heart-shaped leaf scars where other leaf stalks have already fallen off below the buds.

Horse chestnut trees are also known as horsechestnut, common horse chestnut, and European horse chestnut. The scientific name Aesculus hippocastanum literally means horse (hippo) chestnut (castaneum). These trees have beautiful flowers in the spring: check out these pictures.

Prior to taking the photos for this post I had never really noticed the bark of horse chestnut trees. Beautiful! Like carefully sculpted scales, the greyish brown outer bark of the tree I observed was home to moss, lichen, and ferns.

Horse chestnut tree trunk. One side of the tree had reddish bark, the other side was very grey.
Moss and lichen on a horse chestnut tree trunk.
A close up of the intricate scales of a horse chestnut tree’s bark.
Some ferns growing on a horse chestnut tree.

There are other chestnut trees in our neighbourhood. Chinese chestnuts (Castanea mollissima) are edible as they are members of the sweet chestnut family, but the fruit (seeds) are protected by “a spiny whorl of bracts” (Flora, p339).

A collection of Chinese chestnuts from last fall. Unlike the horse chestnuts, these did not open up and fall apart on their own.
Left: Chinese chestnut with one seed out of the case. Right: horse chestnut conker with three parts of the prickly case.

So, get outside, look up at trees for palmately compound leaves and down at the ground to find yourself some interesting but inedible horse chestnuts!

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April 23, 2021

Walking around this week I noticed the horse chestnut trees I photographed in November are now getting ready to bloom. They have towering flower buds and drooping baby leaves. Also, there are baby chestnut trees in garden beds and planters everywhere! If you tug them out you will see that they have a chestnut attached.

Someone (or some squirrel) buried some horse chestnuts in this garden planter last fall and now they are sprouting. (Look in the front centre for the typical palmately compound drooping leaves)

 

Flower buds and spring leaves of a horse chestnut tree in late April.

 

Looking up, it’s hard to believe that these were bare branches a few weeks ago.

 

 

Books I used:

“Aesculus Hippocastanum.” Vancouver Tree Book: a Living City Field Guide, by David Tracey, Pure Wave Media, 2016, pp. 118–119.

“Aesculus.” Flora: over 20,000 Plants and Their Cultivation Requirements, Firefly Books, 2003, pp. 106–107.

“Castanea.” Flora: over 20,000 Plants and Their Cultivation Requirements, Firefly Books, 2003, p. 339.

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