Tuesday, February 21, 2023

The Horse Chestnut Tree (Aesculus hippocastanum)

Today I'm going to talk about the horse chestnut tree.  This tree is not native to North America.  However, it has been planted very frequently all over eastern Canada for hundreds of years, so horse chestnuts can be found throughout Canada, both in urban settings and in rural landscapes.  The tree is also known as the European horsechestnut, the Spanish chestnut, and the conker.

We have an old horse chestnut tree in our driveway.  It probably won't last too many more years, but for now, it continues to provide a lot of conkers each year.

 


Horse chestnuts are widely cultivated in parks and in streets throughout the northern hemisphere, if the local climate is suitable.  They can be found especially widely in temperate parts of the Commonwealth.  Within Canada, they can handle moderately cold conditions, thriving as far north as Edmonton.

One very visually appealing feature of the horse chestnut is the flowers in the spring.  "Inflorescence" is a botany term referring to either the process of flowering, the arrangement of flowers on a plant, or to the complete flower head of a plant (including the stalk/stem, bracts, and flowers.  The inflorescence of horse chestnut comes in a pyramidal shape, with white flowers that have red and/or yellow spots.  Horse chestnuts are very picturesque in the springtime.  Here's a photo:

 


The other distinctive thing about a horse chestnut is the seed, a nut.  The seeds are a glossy brown, and they're called conkers.  I love these things.  You could even go so far as to say that I'm bonkers for conkers.  Now before I go any further, I'll clarify that I don't eat them!  Horse chestnut conkers contain a toxin called aesculin.  This chemical will make a human ill if they eat conkers.  The same applies to dogs and horses, although some animals, such as deer and wild boars, are able to eat them with no negative effects.  And there's a red squirrel living in my backyard that simply loves nibbling on conkers.  I see him sitting on my back porch, week after week, snacking away.

Here's a photo of a box of conkers that we've collected from our driveway tree:

 


Conkers grow in green shells which eventually turn somewhat yellowish-brown.  These green shells have spikes on them, which are fairly prickly, but not especially difficult to pick up.  Here's a photo showing a conker shell:

 


As always, here are some Fun Facts about the horse chestnut:

1.  It's a symbol of the city of Kyiv, the capital of Ukraine.  Incidentally, I've visited Kyiv, and it's a beautiful city with wonderful people.

2.  Horse chestnuts were always an important part of Bavarian beer gardens.  Before refrigeration was common, brewers would dig holes in the ground to keep their lagers cool.  The best way to keep the ground especially cool was by keeping it shaded throughout the summer months, so the brewmeisters planted horse chestnuts, as these trees had a wide dense canopy which cast a strong wide shadow on the ground.  Horse chestnuts also have shallow roots, which were less likely to disturb the beer cellars in the ground.  Bavarian beer "gardens" therefore were usually horse chestnut gardens.

3.  The Anne Frank tree in Amsterdam, known globally for its place in The Diary of a Young Girl, was a horse chestnut.  Before that tree collapsed and died in 2010, descendants of that very tree were planted in prominent locations all over the world.


Although the horse chestnut has essentially become a naturalized tree in Canada, it is not considered a native species.  Therefore, we don't plant it very often.  But there is a home for the horse chestnut in some of our projects, so we've planted quite a few seedlings that we've grown ourselves.  We've also gathered approximately three thousand conkers that we planted directly on a couple of test sites, and we're looking forward to doing surveys in a couple years to determine how successful that work was.

Here's a photo of one of our horse chestnut seedlings in the fall, just as the leaves are about to drop before planting.  Being true Canadians, we were growing them in discarded Tim Horton's cups:

 


 

Thanks for reading!

- Jonathan Clark


Replant.ca Environmental is a Canadian company that plants trees for carbon capture and builds community forests.  We also plant trees in national, provincial, and municipal public parks to mitigate damage from wildfires, storms, insects, and forest diseases.  We operate thanks to numerous small contributions from the general public, in addition to larger project sponsorships from businesses and corporations around the world.  If you'd like to learn how to show your support, visit our donations page.  Even if you aren't able to make a contribution, we very much appreciate when people are able to share our posts or our website link on social media, to help spread the word about the work that we're doing!

To learn more about the various species that we plant, visit the conifers page or the deciduous (hardwoods) page on our website.  Thanks so much for your interest!

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