Field Mushrooms and Their 'Friends'

Just about the only edible mushroom that has popped up this autumn so far is the Field Mushroom Agaricus campestris (Fr. Rosé-des-prés). It's a close relative of the button mushrooms you can buy in the supermarket (Agaricus bisporus), and like many Agaricus species, is good to eat. You do have to be careful though, as the most abundant Agaricus in the Touraine is the toxic lookalike, the Yellow Stainer A. xanthodermus (Fr. Agaric jaunissant).

Field Mushroom in the grass verge of one of the carparks in the Foret de Preuilly.

Agaricus species in general are easy to recognise as they have salmon pink gills, which turn brown with age. This means you should be able to avoid poisoning yourself with any of the much more dangerous pale capped white gilled mushrooms even with beginner skills. The worst that will happen is a trip to hospital with severe gastric problems if you mistakenly eat pink or brown gilled Yellow Stainers. Painful and deeply unpleasant, but you will recover. On the other hand, my advice is never eat a white gilled mushroom. Some of them can kill you.

Young Field Mushroom. Note lack of staining except for a very faint blush on the stem or where the flesh has been broken.

There are nearly a hundred species of Agaricus in France, they all look very similar, and some of them are toxic, so unfortunately it isn't just a matter of merrily eating any mushroom with a pale cap and flesh, and pink gills. The Yellow Stainer is responsible for the most poisonings of any mushroom in France, because of its resemblance to Field Mushrooms and because foragers often don't check diligently enough. Usually the telltale yellowing will quickly appear on any part of the mushroom if you scratch a Yellow Stainer, but sometimes the yellow staining is only present in the base of the stem, which is a bit that inexperienced foragers often leave in the ground. Yellow Stainers don't smell nice and mushroomy like Field Mushrooms either. They smell of phenol or iodine, and it should be obvious when you cook them, even if it wasn't in the field.

Field Mushrooms in perfect condition. Note pointed stem and salmon pink gills on the inverted one, and the silky white cap of the one still in the ground.

It is worth remembering that while most other species of Agaricus are not toxic, Yellow Stainers are not the only Field Mushroom lookalike that you need to beware of. Field Mushrooms are by no means as easy to accurately identify as many foragers believe.

Field Mushroom.

As the name suggests Field Mushrooms grow in fields, gardens, pastures and grasslands in lowland France, especially those where cattle or horses graze. But so does their toxic lookalike. The caps of Field Mushrooms are whitish, between 4 and 10 centimetres across. They start off hemispherical, and stay convex for several days then become flat after a time. With age the entire mushroom goes browner. The stem is white and tapers to a point. There is a stem ring but it is fragile and may disintegrate quite quickly. Where you find one Field Mushroom you will normally find others as they grow together in small groups. The species is present worldwide. Its main growing period is August to November, but you can sometimes find them in the spring.

Field Mushroom.

There are four important criteria for determining Agaricus species: 

• Cap - what does it look or feel like eg smooth? scaly?
• Stem ring - fragile? thin? thick? skirt-like? tooth-edged? 
• Stem shape - bulbous? coming to a point? cylindrical?
• Odour - mushroom? aniseed? bitter almonds? phenol? iodine?

Field Mushroom. Note the thin broken stem ring.

If your mushroom does not meet every one of the characters required (smooth capped, fragile stem ring, stem that comes to a point, mushroom odour) then it is not a Field Mushroom but one of the other Agaricus species. For example, Yellow Stainers have smooth white caps, but their stem ring is persistent and a bit fluffy and flappy, their stem is tree trunk shaped and tends to flare out at the bottom and their odour is an off-putting phenol smell.

Scaly Wood Mushroom Agaricus langei (Fr. Psalliote sanguinolente). Note the strong blush where I've deliberately scraped the stem, the brown scales on the cap, the columnar stem and the more robust stem ring. Grows near hedgerows and on the edges of woodlands. It's not toxic, but not worth eating.

The Field Mushrooms shown in these photos, taken by me last week, were growing with another lookalike species, White Dapperling Leucocoprinus leucothites (Fr. Lepiote pudique). From the top they look just the same and it wasn't until I picked a couple and saw the white gills I realised they were different. In this case the lookalike is not toxic, but they are not tasty enough to bother eating, and in any case, belong to a group of mushrooms that I am very wary of in general.

Yellow Stainer.

An Agaricus I never managed to identify to species level. Not a Field Mushroom anyway, but one of the other species. Obviously you should not eat a Agaricus when you are not of its identity.

This Agaricus may be a Snowy Mushroom A. osecanus, known as the Boule de neige in French. But again, don't eat it if you are not confident of the identification.

Yellow Stainers.

Yellow Stainers. Note the bright yellow appearing where the cap has been deliberately cut, and where the stem has been handled.

Yellow Stainer. Note the bright yellow where the cap has been deliberately cut.

My dear friend and mushroom guru Jean holding an Agaricus sp and regaling us with a story of spending a night on the toilet after having eaten an Agaricus that looked just like this, when he was young and reckless.

Wood Mushroom Agaricus silvicola (Fr. Agaric des bois) is a good edible species. Found in woodland, you need to check it for its strong aniseed scent.