Biodiversity in a kitchen waste recycling bin

Today's Guardian Country Diary is all about the contents of our garden kitchen waste compost bins.

We have been recycling all of the vegetable waste from the kitchen, together with garden weeds and fallen leaves, for about 30 years now, using three black compost bins. During that time we must have produced tons of compost that has all been dug back into the garden, which is now a very fertile plot.

These are some of the organisms that do all the recycling work.

The first organisms to colonise the vegetable peelings and fruit skins are fungi. I suspect that this might be a Penicillium mould, which often grows on the skins of rotting citrus fruits.

This is the rather lovely pin mould, Mucor mucedo, with glassy hyphae and sporangia that look like beads of polished jet.

This, I suspect, is Botrytis, a common coloniser of dead vegetable matter.

Currently there are thousands of these tiny moth-flies (also known as drain-flies or owl-midges) in one of the bins.

They breed in vast numbers during the early stages of composting, when the bins are less than half full....

.... and provide a food source for some of the predators that live in the bins, like this small spider that has an egg cocoon under the bin lid.

The bins are home to a lot of slugs, that consume decaying plant material and are useful all the time they stick to this diet, though in spring they become a nuisance if they consume seedlings in the garden. 

To minimise that risk I raise plants in posts until they are large enough to show some degree of slug resistance when I plant them out in the garden.

A black snake millipedes, that feeds on the decaying plant material and probably on some of the fungi too.

As the composting proceeds and the bin contents become drier the numbers of these minute springtails increase. When you lift the lids they pole-vault into the air, using the special structure called a furcula under their tail end.

And finally ...... the most important recyclers of all, brandling worms Eisenia fetida. When composting is at its peak there are hundreds of these in each bin. 

Much of the compost that ends up in the garden has probably passed through the digestive system of one of these worms.

Under the skin of a sycamore

Thursday's Guardian Country Diary is about the remarkable range of small invertebrates that live under the flaking bark of old sycamore trees.

When the bole of an old sycamore tree expands the old rigid bark cracks and begins to curl at the edges, while ....

.... a fresh, new layer of bark forms underneath. It might not look very attractive but these bark flakes, some as large as a slice of toast, take a long time to fall off and while they are still attached harbour a remarkable fauna of small invertebrates underneath. Here's a selection, most of which I've yet to ID.

Millipedes, a hatched moth pupa and some unidentified cocooons 

Lots more millipedes - these were just a few from under two bark scales - if this sample is representative there must have been hundreds sheltering under the bark of this tree

A minute scarlet mite

A rather beautiful little money spider, Gonatium rubens

A huddle of earwigs ....

... that raised their tail forceps in defence when they were suddenly exposed to the light. Male left, female on the right.

A spider that lives in a silken tent under the bark

Lots of slugs in areas where the bark is permanently damp, where rain water trickles down the tree trunk ..

.... together with snails ......

...... and woodlice

Another moth pupa, that looks as though it hatched successfully.


Sycamore sits low in the league table for tree foliage that supports insect biodiversity - a 1961 research paper on the subject found only 15 species, compared with the 284 hosted by oak (click here for details). But a quick look under the flaky bark of old sycamores casts them in a more favourable light, as a sheltered habitat for a host of invertebrates. 

The few examples shown here were just from a height that I could reach - there may well be a different array of species higher up the trunk and the hosted species most probably vary depending on the aspect (sunny & south facing or shaded & north-facing). Moisture must play a role too because there are well defined runnels where rainwater flows down the trunk from the branches and the bark there is always moist and often very wet. All in all, flaking sycamore bark is probably quite a complex habitat, with many interesting interactions between species that inhabit it.

The Year of the Slug?

I hadn't really realised what an amazing summer this must be if you happen to be a slug, until we went out for a walk after heavy rain a couple of days ago. The footpath was covered with these slimy molluscs, but so too were the flower umbels of hogweed. Wet weather seems to encourage slugs to climb tall flower stems to feed on petals and pollen. Why do they bother, when there is so much food at ground level?

This rather colourful local variety of Arion ater, with an orange skirt, had climbed a dandelion stem to feed on the florets.

Meanwhile, the same rain storms have done serious damage to pollinating bees. This bumblebee was so saturated by rain that it was diffcult to decide what species it might be.

A Glass Half-full kind of Summer....

.... a glass half-full of rainwater, that is.


I should be sitting in the garden sipping chilled wine now, not watching rain running down the window.

And this rain-spattered drone fly should be hovering in a shaft of sunlight. Still, it's an ill wind that blows nobody any good, and .....

..... these house martins have plenty of mud available for nest construction. They were collecting mud around this puddle near Tunstall reservoir in Weardale yesterday. Seems very late to be building nests - I wonder if they were collecting it for nest repair?

Perfect weather for slugs too. I shudder to think what they are doing to my garden, but this one was demolishing a buttercup flower in the road verge.

Good weather for fungal growth too. These brackets were on a dead branch in Backstone Bank wood near Wolsingham.

And good weather for ducks, like this mallard surrounded by rain-bejewelled grasses.

And the raindrops do make an attractive pattern in the shallow water around the edge of Tunstall reservoir.


Accentuate the positive, as the song says....

Midnight Rambler

If you wake up thirsty in the middle of the night and go into the kitchen in bare feet, to get a drink of water, and find something squishy between your toes the chances are it may well be one of these. Yellow slugs Limax flavus are very common in cellars and kitchens.

These large slugs are almost always associated with human habitation but because they are nocturnal many people don't realise they share their homes with them. In this photo you can see the large air pore - the pneumostome - that leads into the animal's mantle cavity, a primitive lung.

The moist, cool conditions of a kitchen at night suit it perfectly, especially if there is a smooth tiled floor to glide over - and it'll probably head straight for any vegetables that might be stored in a convenient place. As dawn breaks it'll glide away again, maybe behind the washing machine or under the sink

This is a slug with a distinct 'hood', from under which two pairs of tentacles protrude.

Although they are quite large the body is very compressible - slugs have a fluid-filled body cavity (a hydrostatic skeleton) where contraction of different muscle layers can make them long and thin or short and fat in any part of their body, so they can squeeze through small gaps - after checking out what's ahead first with those eyes on stalks.

Fully extended, they are up to 10 cm. long.

When yellow slugs come out for a midnight ramble they'll explore every nook and cranny while the rest of the house sleeps, so remember, when you stagger, bleary-eyed into the kitchen for a drink of water at night - they like the feel of smooth, cool ceramic tiles under their feet as much as you do.......

More slugs here

Slither, Slither....

Whenever gardeners gather together in spring, sooner or later the conversation comes around to slugs, those destroyers of horticultural dreams. So, bearing in mind the words of the 6th. century BC Chinese military strategist Sun Tzu - "If you know both yourself and your enemy, you can win a hundred battles without a single loss" - here are pictures of two of the worst offenders. Double-click for larger images. First up, the netted slug Deroceros reticulatum, which so often crawls into lettuces. The colour can be quite variable but this pale grey and buff form is common in my garden, but...

... the ID character that gives this slug its common name is the dark network pattern on the tail end of its body, which you can just see in this view, at the back of the animal.

And here's another slug that will be slithering out in search of tender young seedlings as soon as mild, moist spring days arrive. This is the Budapest slug Milax budapestensis. In this view you can see the open breathing pore (the pneumostome) that leads to the slug's lung. Those little parasitic nematodes that you can buy to kill slugs, as an environmentally-friendly alternative to slug pellets, crawl in through there, breed and kill their host.

The Budapest slug has a distinctive yellow keel that runs along the top of the rear half of its body.....

... and the pneumostome is located towards the back of that 'saddle' at the front of the body, while.....

... the dark stripe that runs along the underside of the foot is also a distinctive feature.

One of my project students, Jack Brooks, is currently investigating whether there are any natural extracts from plants that might be used to deter slugs (they are supposed not to like garlic, coffee and extracts of ivy leaves) that could be used to protect vulnerable seedlings in spring. He's also looking at which garden slugs are damaging and which are harmless to plants - the leopard slug (sometimes called the great grey slug) is supposed to be blameless as far as damage to garden plants is concerned. We'll report back on how the research goes....