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

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?

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 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.

I've used the chestnuts,

I've used the chestnuts, spikey things off and seems to work. Also have found that peppermint oil sprayed around doors, windows etc, have kept them out. There are a lot of things you can use that are not harmful to kids or pets.

I think it's to do with a

I think it's to do with a chemical in the chestnut wood, not the chestnut itself. I've never heard anything about chestnuts keeping spiders away, but I HAVE heard that they won't attach their webs to chestnut wood beams. Maybe that's the source of the story?

I've tried chestnuts, with

I've tried chestnuts, with holes drilled in them, with zero effect. The spiders will even attach webs to them. I suspect the effecacy of chestnuts is more of a seasonal coincidence. By the time the chestnuts fall, the worst of the spider invasion is over.

I live in the countryside and

I live in the countryside and I have had a huge amount of spiders this year, couldnt find conkers, i have now. i had very few last year due to putting conkers in places they tend to enter, ive found it really helps!

When we first moved to BC

When we first moved to BC someone told us about chestnuts being able to rid a house of spiders. We have chestnuts in wicker baskets all over the house, garage and crawl space. Does it help - well, our neighbors have spider problems and we don't - so, we will keep putting chestnuts in our house.

I know from trying it that

I know from trying it that horse chestnuts do not work. I also had recommended to me peppermint oil, which I'm trying now, however, looking on the net, there are many brands of non-harming spider repellent which I'm about to try out- I don't mind the spiders, but their webs are a nuisance in my workshop!

I have used conkers around my

I have used conkers around my house last 2 years! Used to get massive spiders everywhere.....judder, judder!! Since using conkers I've not had even one big spider! They have had no effect on harvester spiders though, although I can tolerate them!! :)

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.

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

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 :-)

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.

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

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?

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?

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....

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