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 love spiders, most don't

I love spiders, most don't bite, most are harmless. I have the most fattest spider in a web in my garden, I catch moths by leaving the porch light on and swatting them and chuck them in the web. Luuuurvly watching a fat spider munching afat juicy moth. The spiders body is now one inch round and growing and his legs are getting real hairy and his eyes glow orange in the dark when Ishine my torch on him at night! Cool or what?

Does anyone in Victoria know

Does anyone in Victoria know where to find a horse chestnut tree??

All over the Fairfield area,

All over the Fairfield area, Cook Street and side streets off of it.

They are all alongWindsor Rd

They are all alongWindsor Rd by Windsor Park Oak Bay. Not quite ready to fall. Good luck

Used to get lots of spiders.

Used to get lots of spiders. For the last seven years I have put conkers about the house, since I have been doing this spiders are gone maybe one or two a year august time. Change every September.

I work in many houses where

I work in many houses where spiders are a massive issue. I love and respect spiders. As long as they respect me! I pick them up (to about half an inch) after that i catch them (glass) and release. I use a pure chestnut oil spray around my bed every month (im still traumatized by having a spider on my face years ago) The houses where i work use the conker/horse conker method... AND the spiders make great webs around them, and hide under them!

I'm dubious.. A lot of the

I'm dubious.. A lot of the comments in here saying that this works also mention that you need to renew them once a year at least. THs makes me think people are mainly seeing spiders at the time of year when conkers are available, which with a lot of species times nicely with mating season when they come out into the open more often, but on,y for a while. As such seeing them and you thinking you need new conkers. When you put the new ones down, mating season is done and so are the spiders, until next time.

I trapped two very large

I trapped two very large spiders Tuesday night. I had never heard of the conker theory until Wednesday. I happened to come across some conkers that same day. When I got Home I slipped one into the glass with the larger of the two spiders. Today the spider with the conker is dead. I do not think it was lack of oxygen, spiders can last under a glass for days, posibly even weeks. Two of the spiders legs looked like they could be slightly trapped under the glass. Can spiders die from injurys?


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