This area of research concerns the fungi that grow in the woody mulch put down by gardeners around shrubs as weed suppression. "Boring" I hear you think - familiar wood decayers growing in manicured gardens. Think again! It seems that the combination of deep woody litter and regular disturbance provides a habitat with no natural equivalent, so that the fungal community which appears is unusual. Indeed, a visit to a large, old bed of woodchips in late autumn will find them covered in large numbers of "rare" toadstools, seldom or never found in native European ecosystems.
In the absence of formal research, I have to rely on casual observations and a natural historian's intuition. It seems to me that there are a couple of 'indicator' species which say "woodchip community" in the same way that bluebells and wood anemones say "ancient woodland" or nightjars and dartford warblers say "ancient heathland". These species are Stropharia aurantiaca and Psilocybe cyanescens, shown in Table 1 below.
Table 1 The definitive woodchip species.
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Psilocybe cyanescens growing on woodchips in Surrey. Note the wavy cap edge and bluing on cap and stipe. The coin is a £1. Confusingly, this used to be known as Hyphaloma cyanescens, and was first described (by Wakefield) from specimens growing in flowerbeds in Kew Gardens in 1946. It may have come from the Pacific northwest coast of the USA, although there is some uncertainty about cystidia on the gill faces (scarce or absent in type material, but found by Paul Stamets to be abundant in Pacific NW specimens). Said to be rare, in the field guides which bother to mention it at all.
Like most members of the genus Psilocybe, this species contains the psycho-active alkaloids psilocybin and psilocin (respectively 5-phospho and 5-hydroxy derivatives of N,N di-methyl tryptamine). Beware: UK law states that although the fungus itself is not prohibited, any preparation renders it into a class A drug. The nature of the "preparation" is not defined, so that drying or even mounting in lactophenol could be covered. Should you chose to ignore this, still handle with immense respect: each of these mushrooms packs 5 times the alkaloids of the more familiar "magic mushroom" Psilocybe semilanceata. There are several anecdotal reports of non-standard effects off this fungus (serious illness in young kids, and genuine hallucinations off high doses, in which contact with external reality is temporarily lost) which suggest substantial doses of other alkaloids. As usual with Psilocybe, symptoms vanish without after effects in 8-12 hours. Clones vary - the Leatherhead roundabout clone hardly blued at all, while specimens from Kew have been almost luminously blue. Finally, note that if you confuse this fungus with Galerina marginata, you give yourself a slow, painful death. |
Stropharia aurantiaca. This distinctive orange-capped
fungus sometimes forms dense clumps of many hundreds of fruitbodies in
ornamental flowerbeds, and is one of the few fungi that can be identified
by eye from a passing car! Despite this field guides call this a
rare species, reflecting its scarcity in natural ecosystems. This
may have first been described as Psilocybe cereus from Australia,
but if so it has adapted itself admirably to UK winters. No-one seems
to have tried eating it, but the lack of a blueing reaction suggests psilocybin
alkaloids to be absent. Some Stropharias are edible (S. rugusoannulata
is sold commercially), others give a stomach ache (S. semiglobata).
I'd love to hear of culinary experiments, but would not advise anyone to
try it out (at least no-one I care about)!
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Table 2. Miscellaneous other woodchip fungi.
 Clathrus archeri
"Devil's fingers'. This bizarre-looking fungus is native to Australia
and Tasmania, but can be found in woodchip beds in the southern UK.
The pale specimen (left) is the clone found in the bamboo beds of Kew gardens.
(Actually the island beds near the bamboos, not the main bamboo display).
Other clones found in the UK are much more scarlet - see below.
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Ramaria sp?. This was thought to be Ramaria stricta
until Aleck Henrici at Kew looked at the spores. These are substantially
too small for R. stricta, but we don't know what it actually is.
Latest suggestion is R. decurrens (an old name which lacks type
material). Whatever this fungus is, it is remarkably vigorous.
It covers some woodchip beds at Wisley and Kew in ridiculous profusion,
maybe 50% ground cover over many square metres! It looks like a curious
ground-cover plant.
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| This one defeated me totally, growing in woodchips at Wisley gardens.
What threw me was the pink spore print, and the fact that it was quite
unlike any of the pink-spored genera in my guides. If a lifetime
of house-dust allergy hadn't blunted my sense of smell, I should have noted
the odour of fish and cucumber. It is in fact Macrocystidia cucumensis,
a member of the Entolomatacea (as befits its pink spores). Again
an oddity - my oracle Geoff Kibby had not found it, although he had been
shown specimens from woodchip beds at Kew gardens.
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Clitocybe cf nitrophila
Yet another taxonomic problem, this densely tufted Clitocybe is widespread in Wisley and Kew - but the colours are different, browner in Kew and greyer in Wisley. One familiar species, or two unfamiliar?
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| Tubaria furfuracea
A common little decayer, that can be found virtually any time of year.
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Psathyrella: There are many of these, and they do cause
taxonomic problems. This is probably P. conopilus.
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The Leatherhead roundabout saga:
On my way into work each day I pass a small roundabout on the A244 near Leatherhead. It was landscaped in 1999, and heavily mulched with woodchips. In May and June 2000 a crop of fungi came up, which I checked carefully (with the aid of Geoff Kibby). There were four species: small numbers of Agrocybe praecox and Volvariella gloiocephela, plus 2 less common species, Agrocybe putaminum (in vast numbers: many hundreds in an area approximating to 50m square) plus Psilocybe percevalii. In fact these other 2 species were third record for the UK and first record for the BMS database respectively! This was such a remarkable combination that I asked the council where the woodchips came from. They put me onto the contractors (Fountain landscapes), who told me that the chips were supplied by County Woodchip Company (Ipswich). I hope to visit their woodchip stockpile some day.
Table 2. Fungi from the A244 roundabout.
| Volvariella gloiocephela (=V. speciosa).
Note the bag (volva) at the stem base. Edible, but it is good advice
to be cautious with any species emerging from a volva as this is a feature
of the deadly Amanitas.
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Agrocybe praecox. This is a common vernal (spring) - summer
fungus that I have seen on several woodchip sites.
The specimen below has prominent blue stains, which leads to a dreadfully embarrassing story. I picked these from the A244 roundabout on my way into work one day, put them down in my car, then later noticed this intense - almost luminous - blue staining. Blue staining in saprophytic fungi almost always means Psilocybin, with an apparent corrrelation between blueness and alkaloid content (though this has never been satisfactorily explained at a chemical level). I assumed that these blue marks showed a super-high psilocybin content. No, I didn't eat them, I checked their ID with Geoff Kibby - who spotted something was dreadfully wrong. It turned out that one of my kids had broken a blue pen in my car, but since the ink leaked onto a black surface no-one noticed. I then put the (moist) fungi on top of a dried-up blue ink stain....
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Agrocybe putaminum. The discovery of this fungus was the
second official record for the UK, with all previous records from Kew gardens.
(Actually Geoff Kibby found some in council bedding in the Wimbledon area,
but no herbarium specimens were lodged). It may be an american species.
Unlike other Agrocybes it has a rough stem with no ring. It was remarkably
prolific, with clumps far too dense for accurate counting to be realistic.
I estimated c. 500 fruitbodies in 3 woodchip beds totalling around 50m2
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Psilocybe percevalii. This is a scarce fungus - its appearance
in Leatherhead is the first entry in the BMS database, though it is probably
not the first UK record. Despite its name, it seems awfully close
to Stropharias such as S. hornemanii. It was obviously more
palatable to animals than the Agrocybes, since all these were riddled with
maggots and scraped by slugs within days of emergence - it was hard to
find usable specimens - while Agrocybes stayed intact, to dessicate after
about 2 weeks.
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And here is what the Guardian made of the woodchip fungi story!
Other species that I've encountered in casual poking around ornamental beds: (This list is tiny and will certainly expand).
Agaricus augustus
Armillaria ostoyea (maybe coming up through from underlying
roots)
Collybia butyracea
Coprinus picaceus
Gyromitra esculentea
Lepiota rhacodes var hortensis (in glasshouses)
Lepista saeva & L. sordida
Mycena spp
Research questions:
There are many research questions that arise out of this community,
a few of which I hope to sort out in the coming years.
Nature of the substrate: I am sure that different
mulching materials give rise to different communities. Pine-bark
chips give rise to very depauperate communities compared with those found
in wood chips. (The odd little Mycena alcalina, and one clump
of Lepista saeva). How about broad-leaved vs coniferous wood?
Genetics: I am sure that the alien colonists
should have a limited genetic base compared to native species. IN
fact I have a hunch that Stropharia aurantiaca is a clone. All we
need is funding for an AFLP analysis...
Succession: The younger beds at Wisley (post-dating
the 1987 hurricane) have Tubaria furfuracea and Psathyrella
spp. but not much else, while older beds have a species-rich community.
Is this a true succession or random arrivals?
Management: Garden beds are managed in many
ways: chips are scraped aside for fertiliser application, they may be irrigated,
trampled, or topped up with fresh chippings. To what extent do these
practices affect their fungal communities?
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