Darwin's Garden earthworm weekend

Sampling for earthworms in Doctors Field, Shrewsbury

A contemporary cartoon of Darwin

Charles Darwin said of earthworms: “It may be doubted whether there are many other animals which have played so important a part in the history of the world”.  Given the current state of the planet and the ‘Anthropocene’ age we’re living through, I might make a case for humans as the species who’ve had the largest impact on the world, but who am I to argue with the man himself?  So worms it is.

Darwin is of course most famous for his book ‘On the Origin of Species’ which outlined his theory for natural selection. However, in his lifetime the book that sold the most copies was the challengingly titled ‘The Formation of Vegetable Mould, Through the Actions of Worms, With Observations on Their Habits’.  Or ‘Worms’ for short!

Darwin had a lifelong fascination with earthworms.  A cartoon of the elderly Darwin shows him, deep in thought, with a large earthworm suspended like a question mark above him.  So it was a definite thrill to be setting out for a day of earthworm hunting in Darwin’s childhood garden, where the young Charles discovered and honed his fascination with the natural world.

Sign on gate of The MountDarwin was born in Shrewsbury, the son of Robert, a local doctor, and Susannah, part of the wealthy Wedgewood family (of pottery fame).  Luckily for Robert, Susannah brought with her a large fortune with which the couple built an impressive home (The Mount) and extensive vegetable plots and ornamental gardens, some of which sloped steeply down to the River Severn.  They chose Frankwell, at the time a rather un-salubrious area of Shrewsbury, poor and unhealthy and outside the town walls.  This gave Robert easy access to potential clients needing his medical expertise.

‘Team Earthworm’ met for the day in Frankwell – now a desirable residential area at the edge of the town centre – and were joined by Sara Lanyon, a local expert on the Darwin family and their Shrewsbury links.  We spent a fascinating hour tracing the still-visible outlines of the Darwins’ land in amongst the Edwardian terraces that now stand on the majority of the site: a section of old red brick garden wall here, a fruit tree there.  The house itself is now out of bounds, used as offices for the District Valuer.

Darwin's GardenThen we headed into the last remaining fragment of Darwin’s Garden – the wooded, steeply sloping section of old garden sloping down to the river.  The site has recently been purchased by Shropshire Wildlife Trust, who are restoring it and developing plans for its future as an important resource for the local community.

Darwin was a prolific letter writer, and it’s possible (with a bit of speculation) to trace events and descriptions from his letters to certain plants and features in the garden.  Is the large sprawling rhododendron the one proudly written about as ‘one of the first in the country’? Are those tangled blackcurrant bushes the ones Darwin wrote about planting with his sister?  And are those old yew trees the same ones from which the long suffering gardener had to collect seeds from, for the young Charles’ germination experiments?  It’s tempting to think so, and it certainly lends a magic to what would otherwise be a rather unprepossessing area of woodland. The original ‘tangled bank’ maybe?

Learning about Darwin in Doctors FieldAfter exploring the garden, we then made our way to the adjoining Doctor’s Field, named not for Dr Robert Darwin but because local people used to use the area to gather their medicinal plants.  Now a community orchard and nature reserve managed by the Town Council, this area would have formed part of young Charles’ world.

In Doctor’s Field Keiron Brown of the Earthworm Society of Britain demonstrated how to sample for earthworms by digging soil pits.  Splitting into small groups, we carried out this standardised sampling methodology before augmenting it by ‘ad hoc turnover’ searches under logs and in dead wood.

Sampling for earthworms using soil pitsBy this point the chilly and damp October weather was beginning to take its toll on our spirits!  We headed back to the shelter of Darwin’s Garden, for some fast and furious earthworm sampling – mainly turnover and leaf litter sampling here.  It was incredible to be sampling for Darwin’s favourite group of animals on paths trodden by his feet.  Earthworms collected, we headed back to Preston Montford field centre.

The following day was devoted to identifying the earthworms.  Keiron gave a brief introduction to earthworm ecology, before running through the key features of earthworms and how these are used in species identification.  After that, it was over to the participants – furnished with microscopes, forceps, petri dishes, alcohol and earthworm keys, they began keying out their first specimens.

Earthworm ID is not too tricky, although as with anything practice makes perfect (usually!).  There are relatively few features on the outside of an earthworm, and it is usually a case of careful counting which segments these features fall on.  The shape of the head, and the groupings of setae (small hook-like hairs) around the body are also important.  Examination of these features allows the worm to be identified as one of the 29 British species...in theory anyway, as there’s always the odd ‘funny worm’ around!  We used the FSC's Earthworm Key.

Identifying earthwormsMore than 100 years ago Darwin recognized the importance of the ecosystem services earthworms provide long ago.  He wrote: “Without the work of this humble creature, who knows nothing of the benefits he confers upon mankind, agriculture, as we know it, would be very difficult, if not wholly impossible”.  It is therefore strange that we know so little about earthworms and especially their distribution.

They are an incredibly under-recorded group for something so ubiquitous.  We found several specimens of the ‘rare’ earthworm Aporrectodea icterica – only the second time it has been found in Shropshire.  There are only 59 records of this species on the NBN Atlas (see map below).  Although the areas we were sampling during the weekend are special places given their significance for young Darwin, the habitats there are not unusual – so it is likely that this species is simply under-recorded rather than actually rare.

We found ten species in total from Darwin’s Garden and Doctor’s Field. These are:

A.icterica distribution (NBN Atlas)

  • Allolobophora chlorotica
  • Aporrectodea caliginosa
  • Aporrectodea icterica (‘rare’; see map left)
  • Aporrectodea longa
  • Aporrectodea rosea
  • Dendrodrilus rubidus
  • Eisenia fetida
  • Lumbricus castaneus
  • Lumbricus rubellus
  • Lumbricus terrestris

The records will be sent to the earthworm recording scheme run by the Earthworm Society of Britain, and shared with the NBN Atlas.

Ten people attended the weekend. It was, for me at least, a fascinating insight into the early life of Darwin.  Spending two days focussed on the creatures that were his lifelong passion made us feel that little bit closer to the great man himself.

Links

Purchase the FSC's Earthworm Key.

Check out the Tom.bio project's Earthworm visualisation and multi-access key.

For more details on earthworms, upcoming courses and events, please see the Earthworm Society of Britain’s website.

For more information on Darwin’s Garden, please see the Shropshire Wildlife Trust’s reserve page.

Many thanks to Shropshire Wildlife Trust and Shrewsbury Town Council for allowing us to sample earthworms on their sites.

Cake - no FSC course complete without it!