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 have had a horse chestnut

I have had a horse chestnut tree for over 40 years and have saved the nuts for spiders, drilled them, cracked crushed them, left them as they fell from the tree. The only thing that happened was the spiders spun webs upend them. All was a waste of time. I live in Osoyoos, British Columbia, Canada

Well, the previous owners of

Well, the previous owners of our house did water chestnut vs spider thingy & now that arachnophobia has taken place, I can see why she did that - soooo, here I go - but I'm not sure if I should drill holes or not but I guess it can't hurt - so my husband is now going to drill holes in the ones that I've placed in the corners of our house - if it works I shall report back :)... Namaste

I'm live in a flat & there

I'm live in a flat & there are big spiders - even crawling onto my bed. I've just been out to collect a bag of conkers. I shall let you know how effective this is or not. I'm desperately hoping it will work as I loathe spiders but couldn't possibly kill them myself. I'd rather leave it to a conker...

Well I believe that chestnuts

Well I believe that chestnuts or as we call them conkers do work. We very seldom have spiders in our house since placing them each year in all corners of the house

It works. I hit a spider with

It works. I hit a spider with a horse chestnut this morning and I knock her down. It really works but you need to be careful as if you not very good with your aim you might break stuff around the house... You might prefer to hoover them.

Put them behind ur filter in

Put them behind ur filter in ur furnace, not on the furnace side of the filter or the blower can suck them up and they bend blower wheel fins. Put them on the return side of the filter and turn ur blower on. Not only does running ur blower constantly extend its life but it will also disburse the chestnuts odor throughout ur house, which we can't smell. I do this and have only had a cpl spiders all year.

We collect conkers and drill

We collect conkers and drill a 5mm hole in each one. They are placed at any location that could allow spiders to enter. Last year placed and no spiders. This year bad for conkers but have collected a few. Will repeat the exercise with the new conkers.

for 2 yrs i've lived here and

for 2 yrs i've lived here and used horse chestnuts around my apartment because I used to see spiders in any of the rooms in my apartment. I've put them on the window sills, on the floors near doorways or anywhere i've seen spiders before. I haven't poked holes in the chestnuts. I also use small bags of lavender around some windows as i've read they dislike lavender. Also ready they dislike any citrus fruit. I can safely say I don't see any more spiders in my apartment. I've put them on my balcony as well. Each year I harvest new chestnuts and i don't really get rid of the old chestnuts. I truly believe they work on the spiders of this area, Victoria, BC.

My host mother put a lot of

My host mother put a lot of chestnuts in my room after I commented that there were many spiders living there. For a while I thought that they were working because no new spiders were appearing, however more spiders came and they made webs above the chestnuts as though as if they weren't there.

Been puting conkrs around my

Been puting conkrs around my house for years & had reduction in spiders but recently found 1 conkrs covered in a cobweb & my grandson sent photo to his mum of a spider sitting on a conkr So are spiders becoming immune to the conkrs? I also spray spider repellent around Windows if I have to open them!

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