The Red Notebook

An unexpected Helix aspersa last Thursday

It isn’t every Thursday morning that one makes a paradigm-destroying observation while rushing, umbrella-in-hand, to one’s car. But that is exactly what happened to me last Thursday. It was pouring with rain, I was running six minutes late for work, I was wet and cross about it, when suddenly, there it was, as bold as brass and as bright wet as day, in front of my very eyes: a common (but, until that point, not at all garden) snail, Helix aspersa, sliming its way across my driveway.

You have no idea how ridiculously happy this made me feel. It is six years this month since I moved to my home in the Yorkshire Pennines, and, in all that time (with one very minor exception), I have seen (if you’ll forgive the inappropriate cliché) neither hide nor hair of a snail. And, believe me, I’ve looked.

I first wrote about the lack of snails in my garden in 2002, in an essay entitled …So Let’s All Be Scientists! It was my contribution to Darwin Day Collection One: The Single Best Idea Ever [ISBN: 0972384405, Amazon.com], a collection of articles, reviews and cartoons in celebration of Darwin and science. In the essay, I suggested a number of hypotheses—some of them more serious than others—why there were no snails in my garden.

Until 06:16 last Thursday, the acidic soil hypothesis (i.e. the acidity of the soil preventing snails from forming shells) was my favourite explanation for the dearth of snails, but that has had to go by the wayside. I am now beginning to favour the out-competed-by-slugs hypothesis. For the first four years that I lived in this house, the garden was literally plagued by slugs: thousands and thousands of slugs. But, for the last two years, the number of slugs has dropped considerably. I’m not sure why this should be—a combination of an unusually dry summer last year, and more dilligent weeding by yours truly is my best guess—but maybe the marked drop in slugs has let the snails get a (literally) single foot in the door. A Darwinian mollusc war in my own garden: who’d have thought it?

I will continue to monitor the situation with renewed interest.

The wild patch in my garden this afternoon

As we are encouraged to do these days, my partner Jen (FCD) and I have set aside a corner of our garden and allowed it to run wild. We call it our wild patch.

OK, if truth be known, it is supposed to be our vegetable patch, but it has got a bit out of hand. The nettles run rampant, the bracken I dumped there last summer to rot away has taken root, and the pile of lopped branches we left there to tidy up later has disappeared under a jungle of grass and raspberry canes. The wildlife loves our wild patch, and so do I. It is my favourite part of our garden.

Peacock caterpillars emerging from silk

This afternoon, as I was noseying around the wild patch, I noticed a mass of tiny caterpillars emerging from a protective silk tent at the top of a stinging nettle. A quick internet search led to Steven Cheshire’s wonderful British Butterflies website, and revealed that the caterpillars were those of a peacock butterfly [photo].

Wild patches are the new black. Why not make your own? It involves (literally) no work at all, and is extremely rewarding. In fact, it’s not entirely unlike being the Duke of York.

Wall Screw-Moss [Tortula muralis]

Yesterday afternoon, I used my sexy, new macro lens to take this photograph of a cluster of what, after a few minutes’ Googling, I discovered to be wall screw-moss [Tortula muralis]. It’s one of the commonest mosses in Britain, thriving in damp, alkaline conditions.

But, as I have recently established, the soil in my garden is decidedly acidic. What’s going on there?

Nature really is amazing. In an area surrounded by acid moorland, the wall screw-moss has managed to find itself a small, alkaline niche in the shape of some concrete slabs on top of my garden wall. As both its English and Linnean names imply, this type of moss is often found on walls. The concrete slabs, and the mortar fixing them to the wall, are manufactured using limestone: a particularly alkaline rock. The moss has established itself along a joint in the slabs, where there is presumably more moisture and better anchorage. Having established itself, it is gradually spreading out across the slabs. It might eventually colonise my entire wall.

My Googling led me to an interesting article about Tortula muralis by UK microscopist Derek Christie. Derek confirmed my guess that the quill-like spikes visible in my photograph are spore capsules. The red tip (calyptra) at the end of each capsule is a protective sheaf for the spore-dispersal mechanism, known as the peristome. In dry weather, the calyptra falls away and the peristome untwists to release the spores. Derek suggests it is this untwisting that gives screw-mosses their names (the word tortula means twisted in Latin).

During my very brief research into Tortula muralis, it occurred to me that, if you put your mind to it, you could probably make a lifetime’s study of something so apparently simple as this small cluster of moss wedged into a crack in my garden wall—or, indeed, any local population of any species you care to mention. Even the simplest of organisms have a grandeur all of their own. The diversity and complexity of life truly is phenomenal—and we have Charles Darwin to thank for explaining how it got to be that way.