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Miranda Hodgson

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Worms have been moving stones in the garden

Posted by Miranda Hodgson on 22 Apr 2014 at 01:51 PM

There are a couple of corners of the garden that I seldom dig – if weeds come up there, I’ll pull them out, but I like to leave these patches to see what happens to the soil surface and to gauge earthworm activity. Because we garden on Oxfordshire cornbrash, there are a lot of stones in the soil and a great many of them end up on the surface. Not only do these stones end up on the surface of the soil, they often appear to be gathered into small piles. When you look more closely at these piles, you can see that there are often bits of plant debris sticking out of the top, usually near the centre of the pile.


So, what’s going on here? I’ve written before about the activities of earthworms and how they gather plant material into piles and gradually pull it under the surface, and it seemed a fair guess that it was worms moving the stones as well. To make sure, I went around the garden with a camera and started to investigate.



 Before I had moved any stones


Sure enough, carefully moving the stones from the centre of the pile revealed a wormhole, the entrance to a worm’s burrow (which is also called a midden). I put down a penny next to the hole to show the size of the stones.



 The midden entrance


Two days later, I took another photograph and saw that most of the stones I’d displaced had been moved back around the wormhole. The same thing happened elsewhere – I’d see a small pile of stones, move enough of them to reveal the midden entrance and go back a couple of days later to find they’d pretty much all been moved back to where they were to start with. It seems very likely that the worms are moving the stones around their midden entrances in order to protect them and stop them being damaged.



 The same area two days later


Piles of stones on the garden beds are not beautiful, but they do give an indication of worm activity and given that we garden on cornbrash, they seem inevitable. And it's also interesting to know how the stones end up in those piles on the surface!

An archive from The Guardian from 1912 also notes that small piles of stones have been moved from a pathway to the edge of a lawn, likely moved by earthworms when the stones fall into their burrows. 


pushkin said:

Fascinating and very informative, especially as the photos demonstrate what you've observed.  Thank you, again.

on 22 Apr 2014 at 02:30 PM

Miranda Hodgson said:

Pushkin, go and look in your garden and see if the same thing's going on. It would be really interesting to know!

on 22 Apr 2014 at 05:04 PM