Written by Raymond Nakamura
Once upon a time, Raymond earned his doctorate studying the hydrodynamics of sand dollars. Nowadays, when he’s not employed as personal assistant to his lovely and demanding daughter, he enjoys creating fun and educational experiences in science and history using facts and fiction, words, pictures and whatever else is handy. 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.

Comments

I'm about to embark on this

I'm about to embark on this drama. We shall see. Frankly, I'm not at all convinced this will work, but I live in hope! I had a fire on my apartment deck in early summer & have recently moved back in to my home. These bloody horrid things are actually leaping about on ME during the night, which means I'm becoming sleep deprived. I know they are because I see them & find their hideous little corpses in the bed after I've slain them with a good healthy wallop. I don't normally murder things at will but this has become war. I hope the few chestnuts I was able to filch away from the squirrels, slobber & all, will help. Before the fire, I had very little issues with spiders, no matter what season.

Although you wrote your

Although you wrote your answer years ago, I wanted to say that I had the same problem with spiders in the bedroom. I solved it this way - a mosquito net over the bed, AND fit muslin squares (which you stick-on all round the window with double sided tape) and NEVER leave the windows open on an August/September evening. Those three things, with conkers also placed near to doors, windows and corners of rooms all year round, will get rid of spiders forever.

There is very little real

There is very little real evidence here. As some have alluded, the variety of chestnut needs defined, the species of spider probably matters. Then where people had spiders and they have gone; was the presence of cheshnuts the only thing. I bet some people moved in and cleaned the house more regularly.

Well My Landlord came around

Well My Landlord came around last week and threw Chestnuts around my patio,telling me they keep spiddies away.A week later I have picked up fifty more and they are all over my new home. I don't think there has been a spider problem but I'm not taking any chances. I live in B.C. and I have even sent a bunch to a friend in Edmonton,A.B. .I do hope these work as I have a Granddaughter who will be crawling soon and that means I will have to remember where I hid most of them before she does. Oops might have been a mistake not to write down where I hid them all.

I have the worst

I have the worst arachniphobia ever.. but for 3 years now I have strewn chestnuts through my house , spiders almost all gone . used to be bad . so , I know it works. they do lose their potency after a while , so I keep a supply in the fridge until next chestnut season-- no one can convince me they don't work

Hi did u drill holes in your

Hi did u drill holes in your conkers or just put then rnd as they where

Have found by splitting or

Have found by splitting or even cracking the shell provides the escape of aromatic scent which appears to have a detrimental deedly effect on all types of spiders, l've watched a spider getting close to a conker then about turn and then curl up and die,

we have found clove oil

we have found clove oil diluted in water in a spray bottle to be effective.not had so many spider's for a while now.spray it at doorways windowsills etc.

Heard about this chestnut

Heard about this chestnut /spider thing on the radio today. When i got home from work i mentioned it to my wife. I was wondering if it was true. She said no and laughed. I said how did she know?. We went into our conservatory and there, covered in cob web from a house spider, was 3 horse chestnuts that i had placed on the window sill. I should also mention that we have loads of webs all over the conservatory, we live in the country and they keep the flies down :-)

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