Written by Raymond Nakamura
Once upon a time (before the Internet), Raymond earned his doctorate studying the hydrodynamics of sand dollars. Nowadays he rents his brain at raymondsbrain.com for writing, cartooning, and thinking, when he is not washing the dishes, walking the dog, or helping his daughter with homework. Follow him on Twitter @raymondsbrain.

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Sunday, October 2, 2011 - 1:56pm

Do horse chestnuts keep spiders away?

While walking our kids to school one morning, I yakked with another Dad about the recent abundance of spiders (he was pulling a web from his hair). He said, "We put chestnuts around our house to keep spiders away." I'd never heard of this before. He acknowledged the weirdness of the idea but insisted on its efficacy.

I crawled around the Web and found various versions of this kind of spider repellent, not only chestnut but also horse chestnut, walnut, or the large round fruit of the Osage orange tree. Still others suggested it was the wood, not the nut or fruit. I did not come across anyone mentioning the spikey casing still on. Maybe people with arachnophobia would just like to believe it would be that easy to keep spiders away.

In Britain, the notion may be more widespread. Their Royal Society of Chemistry held a contest to find the best evidence for or against the idea that spiders dislike conkers, which is what they call horse chestnuts.

The winning entry came from a grade five class from Cornwall. They showed that their spiders did not seem concerned about walking over conkers compared to other materials.

They were lauded for their efforts and sure it's great that they aren't afraid of spiders, but kids these days seem to get patted on the head for every little thing. I did not expect horse chestnuts to have any effect on spider behaviour, but I'm not sure the idea was tested sufficiently, as the Ranger's Blog has pointed out.

1. Not all or even many of the spiders tested would occur in a house. So if the question is whether horse chestnuts keep spiders out of your house, it might be useful to find spiders that would be in your house. Here are some notes about some misconceptions people might have about spiders in BC.

2. Harassing the spiders may not be a suitable test of their substrate preferences. It would take longer, but it seems like you'd have to wait to see what spiders do over time. Something else I hadn't realized before was that household spiders aren't coming in from the cold and you aren't doing them any favours by putting them outside.

3. Horse chestnuts are inedible, which may support the idea that they contain some chemicals noxious to spiders. Some have suggested you need to open the chestnut up or poke holes in it to take effect.

Even if it turns out that horse chestnuts or these other items do not have any effect, I am intrigued as to why people would believe this in the first place. I can imagine a situation where you might happen to have conkers around at the this time of year and the spiders disappear for other, perhaps seasonal reasons.

I have horse chestnut trees all down my street, and I don't have many spiders in my house. If you have a lot of spiders in your house and would like to test chestnuts on them, then let me know in the comments and maybe we could collaborate.


We have put conkers all

We have put conkers all around our house and we are still getting spiders and have had 2 very large ones. So not convinced

Well I don't care what anyone

Well I don't care what anyone says!! I am trying the conckers as we speak. I absolutely hate spiders, I would try anything to get rid of them, nice to see i'm normal & not the only person who thinks they are horrid.

I experienced many spiders

I experienced many spiders UNTIL I put fresh pierced horse chestnuts around the house in small containers and now I rarely see spiders in the mating season or any other time.

Its a myth, sorry, I have

Its a myth, sorry, I have heard this for years and people do seem to believe it but apparently it is merely a coincidence that conkers are in season just as spiders are starting to either die off or hibernate for the winter....

What if I throw the horse

What if I throw the horse chestnut at the spider.... that might work?

I've heard that baked lasagne

I've heard that baked lasagne repels spiders. Just leave a tray of that in a room and the spiders will stay away! Make sure that you use lots of garlic in it!

Hey there! I'm actually just

Hey there! I'm actually just commenting on Facebook that I've used conkers hidden in my flat for 2 years and haven't had one house spider since! Bizarre I know but I'm happy!! Jean, Bedfordshire, UK

This is interesting because

This is interesting because Horse Chestnut capsules, tinctures and cream is good for spider veins...

At both my parents house and

At both my parents house and my own apartment on the outskirts of London, we used to get lots of giant house spiders (that's the species not hyperbole). Maybe 2 years ago we started leaving conkers in the corners of rooms and I have to say as we approach our 3rd September...we haven't seen anything but tiny insignificant spiders since. I would say that the terms "afraid" and "repelled" are unlikely in the case of a spider. I can't remember where I read it but I am sure that I read somewhere that it has nothing to do with toxins in chestnuts as such...more that there is something present in conkers and chestnut bark that blocks or neutralises the "scent" of the female spider. I say "scent" because spiders do not have noses, rather they detect chemicals in the air and surfaces with hairs on their legs. Since in the UK we see spiders mostly in august and September and this usually because male house spiders are out and about looking for a mate, it would make sense if this were true as to why spiders avoid entering houses with conkers as they believe there areally no females present. A friend of mine thinks it is simply that spiders do not like to not have access to the corners of a room and reckons you can put anything in the corners to keep spiders.away. he uses a pile of pennies sprayed with peppermint oil - supposedly another "smell" which interferes with a spider's senses.

We used to get huge wolf

We used to get huge wolf spiders in the house, I'm not scared of spiders and like the thought they keep the flys down! I put horse chestnuts in the corners of the bedroom and have not seen a spider all year, didn't believe it would work but it has for me


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