Mini-autumn in July brings mushrooms part 1

We’ve finally had a decent amount of rain in the days around last Friday’s perigee of the moon. Temperatures have dropped a good 10ºC and it’s feeling a lot like autumn outside. And the mushrooms have responded. They have been coming out in drips and drops since the perigee in June, which was a supermoon, but this week they are out in force.

There are loads of parasols, Macrolepiota procure, and shaggy parasols, Chlorosplenium rachodes, and a whole host of different Agaricus (field mushroom family) and boletes (pored mushrooms).

Parasol, Macrolepiota procera

Everyone knows a field mushroom when they see one but there are nearly 50 species in this family in the UK. The field mushroom, Agaricus campestris, is just one of many very similar looking mushrooms.

Field Mushroom, Agaricus campestris

But this week I have been finding the field mushrooms bigger and more aromatic cousin the Horse Mushroom, Agaricus arvensis. These are distinguished by their “cog-wheel ring” and sweet almond smell when young. As with all Agaricus, rub the bottom of the stem to release the odour.

Horse Mushrooms, Agaricus arvensis, showing the “cog-wheel” ring

The gills of the Horse Mushroom start off a greyish brown colour and are never the bright pink of the young Field Mushroom.

Horse Mushroom, showing the gills

Closely related to the Horse Mushroom and often confused with it is Agaricus fissuratus. This has all the features of the Horse Mushroom but the cap tends to turn a brassy yellow colour as it matures. You can see the yellow colour developing on the buttons in the picture below.

Agaricus fissuratus with the yellow colour of the cap developing

Probably the most distinctive of the almond smelling Agaricus is The Prince, Agaricus augustus. The Prince has the brassy yellow colour of Agaricus fissuratus to the cap but is also covered in orangey-brown scales. The stem is pure white and is covered in fluffy white scales, especially when young. It grows to a large size, often 20cm or more across when mature.

The Prince, Agaricus augustus

Living near the Essex coast we get a lot of the Salty Mushroom, Agaricus bernardii, so called because it grows near the sea, but is spreading inland along road verge due to salting in winter. This is a dense, stocky mushroom, often with a lumpy, irregular shape. It is white, but tends to turn dull and grey with age. The cap often cracks into irregular blocky scales. It has a fibrous almost fluffy ring.

Salty Mushroom, Agaricus bernardii
Salty Mushroom, Agaricus bernardii, showing the fibrous ring

A woodland relative of the Field Mushroom is the Scaly Wood Mushroom, Agaricus langei. This mushroom is found in woods, hedgerows and parks wherever there are trees and shrubs. It is similar to the Field Mushroom in size in having a cap covered in small brown scales. The flesh flesh readily turns red, fading to brown, when cut or bruised. It has a pleasant mushroomy smell.

Scaly Wood Mushroom, Agaricus langei
scaly Wood Mushroom, Agaricus langei, showing gills and stem

Lastly, and only just starting to appear for the first time this year is the Yellow Stainer, Agaricus xanthodermus. This often grows in large numbers and is the main cause of mushroom poisoning in the UK. It is a bright white mushroom (fading to dingy grey when old) that is easily spotted due to the whiteness and abundance. It’s flesh turns a bright, highlighter pen yellow, when bruised. This colour change is only temporary so you need to watch the mushroom for a few minutes to see it develop and then fade away. The speed of the reaction varies with humidity and age of the mushroom. The Yellow Stainer also has a distinctive inky smell because of the toxic phenol it contains. This is best smelt by rubbing the stem base, which is also the best way to see the yellow staining reaction. The ones in the picture below are still very young, no bigger than cherries, but they grow to about the same size as the horse mushroom.

Yellow Stainers, Agaricus xanthoderma. See the scratch mark on the larger cap cap beginning to turn yellow

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