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.


I bought a boat to live on, &

I bought a boat to live on, & I found conkers in every window. I googled it expecting to find it helps reduce condensation, but was surprised to find this spider theory. Well I had plenty opf spiders despite the conkers. I dont mind too much tho, cuz although I'm not overly keen on spiders, they do at least eat the other bugs, flies etc. So the spiders can stay & the conkers have now gone.

they do help how im not sure.

they do help how im not sure..the chest nut,its a really old remedie thats been passed down...could be the smell

It's almost embarrassing to

It's almost embarrassing to read these. Your observation of fewer spiders cannot reliably be attributed to your liberal distribution of conkers, even if you noticed a change post application. Post hoc ergo propter hoc. It may be possible that a change in the number of incidents is related to a correlation between conker availability and mating cycles, or to a change in practice of the observer, but the most likely explanation is that it's all in your heads. It's a placebo and no amount of ritual offerings is going to make the slightest bit of difference. If you want to stop spiders trespassing in your territory then you need to make it very difficult for them to access it. Make sure there are no gaps in your walls, no gaps under or above your skirting boards, coving or architrave. Invest in a fine mesh barrier for your windows and make sure they are sealed around the edges. If you do that, all but the smallest spiders will be blocked, as will the majority of their food. Consider employing a cat to patrol.

Not sure about the conkers,

Not sure about the conkers, but there's one easy solution:cats. I have two and the last few summers we've had zero problems as the cats ruthlessly hunt down every insect or arachnid that ventures into the house. Also plenty of fun to watch:)

Until you disprove the

Until you disprove the affects of horse chestnuts, you don't really know. I am going to experiment with them. There are very large spiders just south of B.C. in my area and filling in the cracks in my house is not going to keep them off my porch. I have to do more. I may give up and just give them collars, names and start feeding them with the rest of the pets. They sure are big enough!

I think a collaboration to

I think a collaboration to gather information would be a good idea. 1. Types of spiders seen. 2. Time of year. 3. Were fresh conkers used? Or old dried ones? Were the husks left on or taken off? A hole drilled? 4. How often were the conkers replaced? 5. How quickly did the spiders disappear? 6. How soon did they reappear? All of this information is important in figuring out just how well something works as a deterrent.

what is effective is i use a

what is effective is i use a well detailed ornament of a spider eating bird like robin or finch and stand it by the opened windows the detail of the bird must be exact like the real thing and spiders stays away from that window, i tested it out because less than 10 feet from my window is a huge spiders nest, and i used in the summer to get 10 maybe 20 spiders a week in my room alone but this summer i tested out a theory and put an ornament of a robbin and seated it by the opened window, i never got one spider so far, not a single one and summer will soon be over my theory worked but the detail of the bird ornament must be exactly like the bird...

I am terrified of spiders, I

I am terrified of spiders, I know it's irrational but can't help it. I heard about the conkers so thought to try it. I don't know how it works but it does, if I get any they are tiny. I have a basket of conkers in the living room like pot porri , and one or two at Windows and doors . One happy lady .

Have used horsechestnuts or

Have used horsechestnuts or conkers for many years as I live in a below ground level basement suite. Suggested it to a friend who is also in a basement suite & my inlaws who live in a house close to a wooded area. We all swear by them, all noticed a decline in large spiders that seem to start appearing in last august. My chestnuts are due to be replaced this fall, as they do get old & dry. I will be harvesting some soon & see if yet again they deter spiders from my living space.

I left 2 conkers on the

I left 2 conkers on the bottom of a ledge Didn't see any spiders. Then a little field mouse took them. It was the only evidence that I had a mouse was in the house, one went missing, then when sitting late one night in the dark a mouse came out taking the other one. Since they have gone I have seen no end of spiders. i really didn't believe it worked but it does. Can't wait for them to drop soon so I can replace them. Spiders don't like them but it seems mice do


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