Slug nibbled Fly Agaric
Slug nibbled Fly Agaric

Mushroom Identification

The below great quote on mushroom identification is saying that there is no easy way of telling poisonous from edible species.

“A toadstool has a cap and a stem and you can’t eat it; a mushroom has a cap and a stem and you can”.

If you want to pick and eat wild mushrooms, the way to avoid risk is to learn the physical features of each species. If globally, people that pick and eat mushrooms recognised 10 of the most poisonous mushrooms,  the incidences of mushroom poisoning would decrease dramatically.

In the UK there are c. 4500 species of mushroom. Even experts can have difficulty identifying some species. For some complicated ones, identification of spores under microscopes or the use of chemical reagents are required. However, with the right approach and some practice, even without such techniques, you should be able to identify a good number of species of fungi.

1. Dangerous Myths

The first lesson is that there are no shortcuts to identifying a mushroom. There are lots of old wives’ tales and myths about safe eating of mushrooms. They are all misleading and dangerous.

Slug nibbled Fly Agaric
Slugs can happily nibble this Fly Agaric. To humans, symptoms from eating it may include apparent intoxication, incoordination, hyperactivity, muscle spasms, collapse, anxiety, visions, and finally, a coma-like sleep!

 

  • I saw a slug / squirrel / deer / rabbit eating it so it must be safe. False
  • If the cap can be peeled it is safe to eat. False
  • Poisonous mushrooms turn a silver spoon / copper coin blue / black. False
  • If silver and copper coins boiled with them don’t change colour, they are safe to eat. False
  • All mushrooms growing on wood are edible. False
  • All mushrooms in meadows and pastures are safe to eat. False
  • All white mushrooms are safe. False
  • Poisonous mushrooms taste bad. False

 

2. Apps can be dangerous

Don’t rely on an app designed to identify mushrooms in the wild using just a smartphone photo. A recent newspaper headline read “Experts Call This Mushroom-Identifying App ‘Potentially Deadly‘”. There are some mushroom apps that are helpful however, see below.

 

3. Books

Mushroom books are great, I have quite a few and could happily buy many more. You can see some of our favourites here. They should be taken outdoors with you to use and not just left on the shelf. Yes, they’ll get wet or dirty, but they are invaluable in the field for correct mushroom identification. However, they need to be used correctly, just thumbing through pictures in a book is unlikely to work.

 

4. The correct process of mushroom identification

There are 4 stages to identify an unknown mushroom – observation, examination, using a key and finally, checking the answer.

a. Observation

You start WITHOUT YOUR BOOKS / APP – with observation about the surroundings of the fungus you are trying to identify:

  • What sort of habitat are you in?
  • What species are the nearest trees?
  • How it is growing? in rings? Singly? in clusters?
  • What is it growing on? Wood (if so what type of tree)? the ground? Dung? Other fungi? Woodchip?
Parasol
Observations about the surroundings: this fungus has been found in grasslands, there are no trees near to it, it is one of a number in a circle and was growing on the ground.

b. Examination

Examine the specimen studying as many fine details as you can think of. Look at specimens in at least two stages of development. This is because they can vary in colour and shape depending on the stage of growth and maturity. The weather will make a difference too; rain will wash-out the colours and make a normally dry cap wet or sticky.

Always gently lever unknown mushrooms out of the ground and handle them with care. This will preserve important characters for identification.

This image shows some of the different structures found under the cap, gill attachment options and cap shapes.

“Mushroom cap morphology” by debivort is licensed under CC BY 3.0

Examine:

  • The cap – size, colour, shape (see above image), stickiness, scales etc.
  • What is under the cap? (see above image) gills, pores or spines/teeth
  • If it has gills, are they crowded or closely spaced ? (see above image) Are they attached to the stem or free? Do they run down the stem (decurrent)? etc.
  • Is there a ring on the stem? what is it like?
  • What is the stem like? Thickness, flexibility etc.
  • What is the base of the stem like?
  • Is there a colour change on cutting or bruising?
  • Does it have a smell?
  • What colour are the spores? In the field you may be able to determine this by seeing where they have dropped onto the cap of another specimen or on the grass / leaf / log below. Often, but not always, the spores are the same colour as the gills. The ideal approach for a definitive answer is to take it home to make a spore print.
Making a spore print

A spore print shows the colour of the spores of any given mushroom. To make one is very straightforward:

• Cut off the stem.
• Place the cap (gills downward) on a piece of paper.
• Leave the cap in place for a few hours.

There are many spore colours including white, cream, pink, purple, brown and black. If you wish to keep the spore print, you can "fix" them with spray glue or hairspray or laminate them.
Mushroom Spore Prints
A selection of spore prints.
Under a Parasol Mushroom
Examination of this mushroom (the same species as in section a above): • Cap – 12 cm across. Mainly white with large brown scales. Centre of cap brown and slightly raised. Not sticky. • Gills are crowded (not close together) and are not attached to the stem. • Large double ring with frayed margin. The ring can slide up and down the stem. • Stem – about 1.5 cm diameter and 14 cm long, thickening towards base, brown and white pattern a bit like a snake’s skin. Stem does not snap if bent. • No colour change on cutting or bruising. • Smell not distinctive. • Spores are white or pale cream.

 

c. Use a key to find out what it is

Keys are an easy to use, valuable tool that are not just used for mushrooms but also for wider species identification (plants, dragonflies, shells etc). The standard approach is to ask questions based on easily identifiable features. Dichotomous keys use questions to which there are only two answers. For example, “Is the cap bigger than 5 cm?”. The key can be presented as a table of questions, or as a branching tree of questions with one answer leading you to the next question. They will include some technical terms but the book will have a glossary to explain them. Some keys will get you to species level, others to the genus. Here is an a short extract from MushroomExpert.Com’s Key to Major Groups of Mushrooms

Question No.QuestionAnswer / Go to question
1.Mushroom growing on other mushrooms or the decayed remains of other mushrooms.Mycotrophs
1.Mushroom not growing on other mushrooms.2.
2.Mushroom with gills on its underside.3.
2.Gills absent.5.
3.Growing shelflike on wood (or, if not, then gills concentric rather than radial); mushroom very tough and leathery, corky, or woody (try tearing it in half); gills tough and hard, sometimes maze-like; cap frequently (but not always) with concentric zones of colour.
Polypores
3Not completely as above.4.

Another key approach is a visual one. The MycoKey MMI ® (Morphing Mushroom Identifier) is a great example. It is described as an innovative identification tool which models your fungus on screen as you enter the characters with automatic presentation of the most likely species. A more detailed version of MycoKey to install on your PC is also sold.

MycoKey

Most mushroom books have a key, people are often unaware that they are in the book or haven’t used them. There are some good App keys too, some being a computerised version of a book’s key. Note that any key will only include the species in that book, not all that you may encounter. For example, one popular mushroom book contains about 100 species of the 4500 or so found in the UK.

Identifying mushrooms can be difficult; individuals of the same species will vary with age and the weather, but a key makes the task a lot easier, far better than flicking though the pictures looking for one that looks right. Give them a go. We teach using keys on our courses and attendees soon get the hang of them, identifying many examples we find.

If you followed a key you would have worked out the the mushrooms shown in the observation and examination sections of this post is a Parasol Mushroom (Macrolepiota procera). MycoKey gives a number of possibilities and ranks how well they fit. You can then “drill-down” to read more about each suggestion.

Parasol Mushroom in MycoKey
Parasol Mushroom in MycoKey

 

d. Check the answer

Check the species that the key has led you to in as many books as you can. Use the pictures and the descriptions. Is every detail correct? Make sure that the descriptions, seasons, preferred habitats and the photographs all agree with each other. If it says only found in the Spring and it is Autumn, you are wrong. Similarly, if it says only found with Oak and you are in an area of just Pine trees, again you are wrong. They may mention “lookalike” species which are worth checking. An Internet search may help in finding more pictures – though there is no guarantee that any picture online is correctly labelled – I am aware of serious errors on reputable web sites!

If the answer given by your key is not like the mushroom your are trying to identify, revisit your key answers in particular any subjective answers like “small”, “bendy” or “sticky”.

One of my “go to” web sites for checking fungi identifications is First Nature. If you look at the entry there for Parasol Mushroom you can check the details of our identification.

 

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