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Loving the Large – Macro Mushroom

We’re at the beginning of summer and have had some decent, warm sunny days and a reliable source of showers – apparently perfect conditions for this summer/autumn Agaric which has shown itself somewhat early. Great news for all foragers who fancy a fry up!

Agaricus urinascensThis small group of Macro Mushrooms (Agaricus urinascens / A.macrosporus) were found on a grassy roadside verge, not far from some fields and a small wooded area. They’re also found in similar environments such as pastures, woodland edges and grassy woodland clearings.

My initial analysis was to rule them out as Field Mushrooms as these are strictly pasture/field bound, away from the tree line. There was no stark, chrome yellow staining as I scored the flesh, so they weren’t Yellow Stainers either. Horse Mushrooms maybe?

Horse Mushrooms and Macro Mushrooms thrive in similar habitats, although the Horse Mushroom is not linked to woodland/tree situations. But they look much the same, especially when it comes to size; with an average cap diametre of 10 – 25cm. It has been known that the Macro Mushroom can grow up to a massive 30cm across – but this humble group were averaging around the 15cm mark.

Luckily, some immediate visual differences set these mushroom heavyweights apart;

The cap of the Macro mushroom is distinctively scaly with many ochre coloured patches. The margin also tends to naturally become toothed and/or split. It rarely opens to become flat like the smooth cap of the Horse Mushroom.

The veil covering the gills on the underside (when young and unbroken) shows a similar cog wheel style pattern as the Horse Mushroom but is not as defined.

The gills are at first greyish-white which then mature to dark brown, unlike the ‘white to pink to dark brown’ colour changes of the Horse Mushroom.

The Stem is distinctly scaly towards the base, and has a delicate/fine white particle coating all over. The stem on the Horse mushroom is relatively smooth.

The odour of the young Macro Mushroom is like almonds, becoming more ammonia-like with age. The Horse Mushroom has a mild aniseed-like odour.

One thing also to note though is that a variety of A.urinascens is also recognised, known a A.excellens. It’s even more of a Horse Mushroom lookalike, but is just as edible. Its cap is much smoother with only minute scales present and it does not grow as large; having only an average cap diametre of 10-15cm.

Edibility

The good news is that all of the above mentioned Agarics, with the exception of the infamous Yellow Stainer, are safe and good to eat. The Macro Mushroom has an excellent fleshy texture – and there’s lots of it. Don’t be put off by the slightly unpleasant, ammonia smell of the mature specimen, this disappears after cooking.

The taste is surprisingly mild although pleasant; similar to the button mushroom supermarket variety (a young variety of Agaricus bisporus). They’re definitely worth eating though. I always make sure I never ‘over pick’ my find and leave several behind to continue in their reproduction. Lovely.

Macro Mushrooms

Agaricus urinescens – The Macro Mushroom – Notice the yellow-brown scaling on the cap and the grainy/scaly base of the stem. The margin will become toothed or even split apart.

QUICK ID TABLE: MACRO MUSHROOM Agaricus urinascens / A.macrosporus

CAP / FLESH

8-30cm across. Initially rounded/convex. Covered in yellow-brown scales. Margin is toothed; often splitting. Smell of almonds in young specimens then has an odour of ammonia as it ages.

STEM

5-10cm x 2.5-3.5cm. Creamy white with fine white particle coating (easily removable); more scaly towards the base.

GILLS / SPORE PRINT

Whitish-grey maturing to dark brown (no pink colouring at any stage).
Spore Print: Brown (see how to take a spore print here).

HABITAT / SEASON

In small groups or even rings in pasture, grassy verges and grassy woodland clearings; summer to autumn

EDIBILITY

Edible. Mild & Good.

The Genus AGARICUS (Wood Mushrooms/Mushrooms): Characteristics to look out for:

• Many discolour yellowish, reddish or pinkish when cut or bruised.
• Those that discolour bright/chrome yellow should be avoided for consumption.
• Gills in young specimens are often pink (white in a few) – maturing darker brown.
• Make note of any smells, such as aniseed or a typical strong ‘supermarket’ mushroom smell.

Horse & Field Mushroom Imposter! – The Yellow Stainer

It’s a Sunday afternoon and I pass by a grass verge near my house. My heart jumps at the sight of a huge cluster of (what seem to be) Horse mushrooms or possibly Field mushrooms, but this is no field, just a grassy verge near trees at the side of the road! I was without a basket or bag so like a kid in a sweet shop I scooped up a good share, leaving some to drop their spores.

But my dreams of a nice fry up or even a creamy mushroom soup are soon quaffed because I suddenly realise these mushrooms are not what they appear to be. I wait until I get home around the corner to double check. Read on…

Image of yellow marking on Agaricus xanthodermus

Chrome yellow staining on cap edge. Bulbous base.

I’m not surprised at all that the Yellow Stainer (Agaricus xanthodermus) is responsible for the most cases of mushroom poisoning in this country. Although this evil twin of our favourite field, wood and Horse mushrooms is not deadly it can keep you in the loo for longer than you normally do! Gastric symptoms can persist for up to 24 hours. Fortunately I have not been caught out yet, but some people after consumption usually get away with only mild upset or sometimes have no reaction at all. My Uncle once told me “Ooh, I don’t get along with those Yellow Stainers – don’t like ’em” . Let’s hope that it was only his palette they offended – I didn’t ask!

So how on earth can I identify this poisonous peril when compared to a Horse mushroom? I hear you all cry!

Don’t rely on the ‘overall look’. They differ in colour from pure white to brown/grey, scaly and smooth, tall and short and so on. Horse mushrooms can display some paler yellow on the cap and stem – so if you do see some yellow it’s not always a bad thing.

Both the Horse Mushroom and Yellow Stainer ‘bruise’ yellow (There’s hardly any yellow about the Field mushroom). But the Yellow Stainer has a stronger chromium yellow once bruised. If you rub the cap with your thumb, there will be a very noticeable colour change. But the crunch test for me is at the very base. Take a knife to the very bottom of the stem (the base is more bulbous than the others) and cut in half (see picture below). If the colour changes to a vivid yellow, then you’ve got yourself a Yellow Stainer. Horse and Field mushrooms do not stain at the base like this.

Other good ID tips are:
1. The smell is an unpleasant (phenol/inky smell more apparent when being cooked)
2. The ring on the stem is large and floppy.
3. Before the veil drops it does not have the ‘cogwheel’ pattern like the Horse Mushroom.
4. Gills when very young are white unlike the Horse and Field mushrooms which are pink

In addition to point 3 – if you’re new to collecting mushrooms, avoid very young specimens as they also can be confused with much more poisonous (even deadly) young toadstools.

The Yellow Stainer - Poisonous UK mushroom

Horse and Field Mushroom lookalike – The Yellow Stainer. Notice the chrome yellow colouring at the base of a cut stem.

Large ring of Yellow Stainer mushroom

On open caps: The ring on the Yellow Stainer is noticably large and floppy. The Field Mushroom’s ring is a fine torn frill. The Horse Mushroom’s ring is formed of a double membrane. The lower part is ‘star shaped’

Quick ID checlist for Agaricus Xanthodermus.

The Genus AGARICUS (Wood Mushrooms/Mushrooms): Characteristics to look out for:

• Many discolour yellowish, reddish or pinkish when cut or bruised.
• Those that discolour bright/chrome yellow should be avoided for consumption.
• Gills in young specimens are often pink (white in a few) – maturing darker brown.
• Make note of any smells, such as aniseed or a typical strong ‘supermarket’ mushroom smell.