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.

Created date

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.


My son has recently moved

My son has recently moved down to our basement which is only semi finished but he wanted more room. Last night he was watching a movie and at the corner of his eye, he saw something moving...it was a spider the size of his palm. He tried quickly to get the broom but it was gone. He said that he was so terrified and could not go to sleep all night. If these chestnuts help, could we get/buy them from you?

Hi there I recently bought

Hi there I recently bought sweet chestnuts from tesco a supermarket chain in UK too remove spiders , try that

I hope you have managed to

I hope you have managed to find another way to get rid of your spiders. I don't really think the the chestnuts make a difference. Anyway I don't have any chestnuts at the moment (Aug). They start coming down in the fall. Good luck!

I've seen them only work on

I've seen them only work on large house spiders. Once in close proximity the spider seems to curl up and die. Once I caught one hovering over a conker on a line of web it was clearly absailing down when the conker repelled any further progress. The spider then brought all its legs together as if trying to be smaller and in less than 24 hours died. Another time a spider had walked past my conker outside my bedroom door and once again stopped it then curled in on itself to such an extent it was unrecognizable as a spider shape once again it died. I should also point out that these conkers I have had for 2 years now!?? I can't imagine anything could really smell that bad??

I have collected horse

I have collected horse chestnuts (confers) for several years and find them very effective. The effect however wears off as they dry out and by then there are no more available. This year I have crushed them up and soaked them in water with a little pectolitic enzyme (used to extract juice from fruit in winemaking). The resultant potion not only deters spiders but, when sprayed onto them kills causes them to ' curl up and die'

Where did you get the enzyme?

Where did you get the enzyme? I would love to know and use a bunch of these combinations of things to keep spiders away. I like the idea of spraying the spiders so they "curl up and die." Thanks.

Yes they do actually but you

Yes they do actually but you must poke a hole in each end. The smell is toxic and they won't come around at all. Also if your dog chews one up it is toxic enough to poison the dog. So anyone with pets that chew please be careful

I have a friend who swears by

I have a friend who swears by conkers... she tells me they need to be drilled once, but last for years. Having grown up on the west coast of BC you would think we would be used to buggies and such, but those big, huge, black, hairy legged, beady eyed monsters scare the pants off us. I prefer Diatomaceous earth, but it has gotten so expensive I am going to try the chestnuts. I will let you know how they work!

I have used chestnuts

I have used chestnuts successfully! We used to get large wolf spiders in our basement suite. I would collect chestnuts drill a hole in them and then place them in corners and where I had previously seen spiders. We didn't get many more after that. I found I needed to replace them yearly.

Yes , chestnuts have worked

Yes , chestnuts have worked for me ! I live in a basement and haven't had any spiders in 2 years. . I do have to replace them yearly but they come free if u go for a walk and collect some in the fall :) In Vancouver B.C They are plentiful..... I believe they work to an extent ! I have chestnuts everywhere !


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