19-Sept Mushroom Magic: London’s Hidden Agarics

When looking at agarics with a view to eating them there are certain rules of thumb that should be followed. Always bruise the edge of the cap and base of the stem or even cut it to see if it turns yellow. An immediate change to yellow is a bad sign. Also, smell the gills; if they smell of almonds or aniseed it is generally a good sign and if you smell ink or iodine it is a bad one. All small agarics are best left, especially if the cap is unopen, as they can so easily be confused with young specimens of highly poisonous Amanita species. Also if the caps are found anywhere near a road they should not be picked as they may well contain pollutants absorbed from passing cars. It is always worth remembering agarics are a bigger group than most people realise with perhaps eighty or more different species, of which perhaps half occur in London.

It is the larger agarics that tend to get noticed, especially the Yellow-stainer Agaricus xanthoderma. This is common in parks and cemeteries and is easily identified when fresh due to it instantly turning from white to chrome yellow at the edge of the cap when bruised. If the stem is sliced in two lengthwise, it also turns the same intense yellow but only at the base of the stem. If eaten it usually causes nausea, but can cause much more serious symptoms, even coma. Large agarics also tend to be found at the sides of road. The two most likely to be seen here are the Pavement mushroom A. bitorquis and the Salt-loving mushroom A. bernardii. The first is quite capable of lifting paving stones as it grows due to the pressure of osmosis and the second is more typically seen by the coast, its presence in London being largely due to road salting. Both are edible, but are far too firm to be easily digestible and should not be picked as they grow in a polluted habitat. As with so many agarics both tend to redden when handled, but only A. bernardii has a fishy smell. Another rarer agaric which may now be seen pushing its way up through the soil is A. vaporarius. Although ugly looking with dark scales covering its cap, it has one of the most delicious odours of all agarics, sometimes described as liquorice.

The species that reddens most dramatically is, as its name suggests, A. haemorrhoidarius which is found in oak woodland. Agaricus silvaticus colours red not quite so much and is found in conifer woodland. A. impudicus, which has a fruity smell, is also found under conifers but only tends to turn slightly pink when it is cut. A. langei also turns a dull pink but has a more spindle-shaped stem. The main edible species that most people are looking for don’t tend to change colour at all, except perhaps slowly to a light soft yellow.

This is especially true of the horse mushroom A. arvensis once found typically in fields where horses grazed but now more likely to be found in gardens. Along with its close relative the Prince A. augustus it can produce caps up to twenty centimetres across with just one specimen being quite sufficient for a good meal. It is occasionally seen in both conifer and deciduous woods and usually recognised by its size, scaly cap, slight yellowing and strong smell of bitter almonds.

One last confusing agaric usually found in conifer woods is the wood mushroom A. silvicola. It is like A. silvaticus but tends to turn a soft yellow rather than red. It also smells of almonds whereas A. silvaticus smells of aniseed. Both are good to eat but with their long, thin stems there is rarely enough to merit collecting. Both these species can be found in the pine woods around Oxshott.

Most other agarics are much smaller, usually not much larger than button mushrooms and difficult to identify in the field. Rarer species include A. comtulus and A. niviscens in grassy areas and A. romagnesi, A. variegans and A. langei in conifer woods.

Before taking the plunge and deciding whether or not to eat any of these agarics or similar-looking Leucoagaric species it is wise to become acquainted with the red-staining Inocybe I. patouillardii as well as the Livid Entomola Enteloma lividus. Both are highly poisonous and not unlike these agarics. The latter mushroom is responsible for eighty per cent of all fungal poisonings in France.