The key

Answer questions about the thing in your hand.

This is how identification is actually done, and it teaches the order in which features matter, which no list of species pages can. Lift the whole mushroom out of the ground before you start. Do not cut the stem: the most important character of the deadliest genus in the world is often underground.

Step 1

Turn it over. What is on the underside of the cap?

Lift the whole mushroom out of the ground first, gently, with the base intact. Do not cut the stem: the single most important feature of the deadliest genus is often three centimetres underground, and cutting leaves it there.

This key never rules anything in. It narrows a specimen to a group and names what in that group can hurt you. Confirming a species depends on characters only the person holding it can see, and on a regional field guide, and often on a spore print taken overnight.

The whole key, written out

Every question, and everywhere it leads.

Useful for reading through in advance, for printing, and for anyone who would rather see the whole structure than be walked through it one question at a time.

Question 1

Turn it over. What is on the underside of the cap?

→Blades or ridges(Anything that looks like gills, whether sharp-edged or blunt)
→A sponge of tiny pores(Fine holes, on a fleshy mushroom with a central stem)
→Pores on a tough bracket(Growing out of wood, leathery or woody rather than fleshy)
→Downward-hanging spines(Soft teeth that rub off with a thumb)
→Nothing. It is a closed ball(No cap, no gills, no stem)
→No cap at all(Branched, club-shaped, brain-like, honeycombed or cup-shaped)

Question 2

Now look at the very base of the stem, where it came out of the ground.

This is the question that saves lives, and it is the one people skip because the answer is buried. Brush the soil away from the bottom two centimetres.

→A membranous sac or cup around the base(Like the mushroom is standing in a bag)
→A swollen bulb with concentric rings or a rim(Not a free sac, but an abrupt bulb with banding)
→Neither. The stem goes straight into the ground, or into wood

Question 3

Look closely at the blades themselves. Try to pick one off with a fingernail.

This separates true gills from false ones. False gills are folds of the cap flesh, so they cannot be removed; true gills are separate structures and lift away.

→Blunt, forking, vein-like ridges that will not come off(They run down the stem and look like folds)
→Thin, sharp, blade-like gills that lift off cleanly

Question 4

Where was it growing?

Habitat is a genuine identifying character, not background information. Several dangerous pairs are separated by nothing else.

→On wood(A stump, a log, a living trunk, or buried roots)
→In grass(Lawn, pasture, park, verge, playing field)
→On soil among trees(Woodland floor, leaf litter, conifer duff)
→On wood chips or mulch

Question 5

What colour is the spore print?

If you have not taken one, choose the last option. On wood-growing gilled mushrooms this is not an optional refinement: it is the only thing separating a good edible from an amatoxin.

→White or cream
→Rusty brown
→Purple-brown or black
→I have not taken one

Question 6

What colour is the spore print?

Grassland holds both the commonest edible mushroom and one of the deadliest species on earth, side by side, in the same weeks.

→Green
→White
→Dark chocolate brown
→Pink or salmon
→Black, or the cap is dissolving into ink
→I have not taken one

Question 7

What colour is the spore print?

→Rusty brown
→White
→Pink or salmon
→Brown or olive-brown
→I have not taken one

Question 8

What colour is the spore print?

Landscaping mulch is its own habitat and moves species around the world on the back of a truck.

→Purple-brown or black
→Rusty brown
→White
→I have not taken one

Question 9

Cut it in half from top to bottom, with a knife, and look at the cut face.

Every ball, individually, every time. This is one second of work and it is the difference between a puffball and an unopened death cap.

→Pure white, uniform and featureless, like a marshmallow
→The outline of a small mushroom inside: cap, gills, stem
→Firm, dark purple-black, marbled with white veins
→Yellow, olive or powdery

Question 10

What shape is it?

→Conical, pitted and ridged like a honeycomb
→Wrinkled, lobed and folded like a brain or a saddle
→A branched coral, or an upright club
→A cup or a disc
→A cream mass of flat wavy ribbons at a conifer base

Question 11

Cut it in half lengthwise, from the top of the cap through the base of the stem.

This is the only reliable test in this group, and the shape of the cap is not it.

→One continuous hollow chamber, all the way through
→Stuffed with cottony fibre, or divided into irregular chambers

Where it can end up

Stop here

This is very likely an Amanita. Put it down.

A membranous sac at the base, or an abrupt bulb with concentric banding, places a gilled mushroom in the genus that causes the overwhelming majority of fatal mushroom poisonings in the world. The genus does contain edible species, and people do eat them, and this is not the place to learn which. Half a death cap will kill an adult, cooking does nothing to the toxin, and the symptoms hold off long enough that people are sometimes discharged from hospital while their liver is failing.

What amatoxin poisoning does

Narrowed down

Blunt forking ridges: the chanterelle group, and its impostor.

False gills that cannot be picked off are a good sign and not a conclusion. The jack-o'-lantern has TRUE gills, orange flesh right through, and grows in dense clusters on wood or buried roots, while a chanterelle grows singly from soil and has pale flesh inside. Cut it open and look at the colour of the flesh, then look at what it was growing out of.

Chanterelle against jack-o'-lantern

Stop here

A rusty-brown spore print. Stop.

Rusty brown covers two things you do not want. On wood it is the deadly galerina, which carries the same amatoxins as the death cap in a mushroom nobody takes seriously. On soil it is Cortinarius, a genus of several thousand species, mostly undescribed, separated by microscopic characters, some of which destroy kidneys with no symptoms at all for up to three weeks. There is no field character that makes this group safe to work through, and the sensible position is to leave every rusty-spored mushroom where it stands.

The three-week delay

High-risk group

White-spored, on wood. A good group, with one trap.

Oyster mushrooms and honey mushrooms both belong here and both are eaten widely. Two things to settle. Oysters should be on HARDWOOD: the thin, pure-white angel wings on conifer was treated as edible until an outbreak in Japan in 2004 killed seventeen people, most of them with existing kidney disease. And honey mushrooms must be cooked thoroughly, because undercooked ones make a lot of people ill.

The oyster specimen sheet

High-risk group

Dark-spored, on wood or mulch.

Wine caps in mulch are here, and so is sulphur tuft, which is probably the most frequently encountered toxic mushroom in Europe and grows in dense clusters on any stump in any park. Sulphur tuft has yellow-GREEN gills before the spores darken them, and it is ferociously bitter. The wine cap has a thick ribbed ring like a cogwheel.

Growing wine caps instead

Stop here

A green spore print is effectively diagnostic. Do not eat it.

Green means Chlorophyllum molybdites and essentially nothing else you are likely to meet. It is the most commonly eaten poisonous mushroom in North America, because it is large, handsome and grows in lawns, and it causes severe vomiting and bloody diarrhoea that hospitalises children in particular. Young specimens have white gills and look exactly like the edible parasols, which is precisely why the print is the test.

Stop here

White-spored, in grass. The most dangerous answer on this page.

This combination covers the destroying angel, which is among the deadliest organisms on earth and grows in grass at the edge of trees, and the small white ivory funnel, which contains more muscarine than the fly agaric does. If you did not lift the whole mushroom and check the base for a sac, go back and do that now. If the mushroom is small, white, funnel-shaped and has gills running down the stem, it is not a fairy ring champignon.

The muscarinic syndrome

Narrowed down

Chocolate-brown spores in grass: the Agaricus group.

This is the genus of the shop mushroom and the field mushroom, and it is a reasonable place to be. Two checks remain. The gills must go PINK then brown, never staying white, and the base must have no sac. Then cut the stem base: the yellow stainer is common in the same fields, bruises bright chrome yellow there, smells of ink or carbolic, and makes people ill.

The meadow mushroom sheet

High-risk group

A pink spore print. A group to be careful with.

Pink covers Entoloma, which contains several serious gastrointestinal poisoners including the livid pinkgill, one of the commonest causes of severe poisoning in Europe. It also covers the wood blewit, which is eaten widely and must be well cooked. The livid pinkgill smells strongly of flour, and so does the St George's mushroom people confuse it with, so the smell separates nothing.

High-risk group

An inkcap. Which one decides whether you can drink this week.

The shaggy mane is a tall white shaggy cylinder and is excellent, provided it is cooked within hours of picking, because it starts dissolving itself immediately. The common inkcap is grey-brown, smooth and clustered, and it is harmless by itself but causes a violent disulfiram-like reaction with any alcohol taken within roughly three days.

The alcohol reaction

High-risk group

White-spored, on soil in woodland. Proceed slowly.

The largest and most difficult group there is, and the one that holds Amanita. If you did not lift the whole mushroom and check the base for a sac or a banded bulb, that question is not optional and you should go back to it. Matsutake, milk caps and many good edibles are also here, and so are species separated from lethal ones by a single character.

Work through the specimen sheets

Narrowed down

Brown or olive spores on soil.

A broad group. Confirm the spores are not RUSTY, because rusty puts you in Cortinarius and that is where the key stops. Beyond that, this needs a regional field guide and the specimen in front of you rather than a web page.

Which field guide

Go and do this first

Go and take a spore print. Everything else waits.

You have reached the point where no further progress is honest without one. It costs a sheet of paper and a night, it settles the honey mushroom against the deadly galerina and the parasol against the green-spored one outright, and it is skipped precisely because it is slow. Cut the stem flush, put the cap gills-down on a sheet that is half white and half dark, cover it with a bowl, and read it in daylight tomorrow.

How to take one

Narrowed down

Pure white and featureless: a true puffball.

Uniform white flesh with no internal structure at all is what you want. Two conditions still apply. Cut EVERY specimen individually, because one Amanita button in a basket is enough. And any yellow or olive tint means the spores are forming and it is past eating, which is a matter of taste rather than safety.

The cut that matters

Stop here

An outline inside means an unopened Amanita. Stop.

The silhouette of a cap, gills and stem inside what looked like an egg is a young Amanita still enclosed in its universal veil, and that is how death caps and destroying angels begin. A puffball has no structure inside at any age. Discard the whole basket if you cannot be certain which specimens you have already checked.

Why the delay kills people

Stop here

Dark and marbled inside: an earthball.

Firm purple-black flesh veined with white is Scleroderma, not a puffball. It causes strong gastrointestinal upset, it is the commonest puffball mistake, and it is occasionally sold to restaurants as truffle. The thick warty rind is the other tell.

Stop here

Yellow, olive or powdery inside: too old, whatever it is.

The spores have started to form, and at that point it is no longer food regardless of species. It is also now much harder to identify, because the interior is exactly what you needed to look at. Leave it: a mature puffball releasing spores is doing the useful part of its life.

Narrowed down

Pitted, and hollow all the way through: a true morel.

One continuous empty chamber from cap to stem base is the test, and it is the only one worth relying on. Morels must be thoroughly cooked, never eaten raw, and even properly cooked they disagree with a minority of people, particularly alongside alcohol. Eat a small amount the first time.

The morel specimen sheet

Stop here

Stuffed or chambered inside: a false morel. Do not eat it.

Gyromitra contains gyromitrin, which the body converts to monomethylhydrazine. It is volatile, it is cumulative in effect across meals, and the vapour alone has hospitalised people who were only cooking it. There is a long tradition of eating it parboiled in parts of Europe, and that tradition is a long habit of gambling with a carcinogen.

What gyromitrin does

Narrowed down

Pores rather than gills: a bolete.

A comparatively forgiving group. No bolete in North America is deadly, and the ones that cause trouble tend to announce themselves: red or orange pore mouths, flesh that bruises blue quickly, or a bitterness strong enough that one specimen ruins a pan. White unchanging pores, a white net on a barrel-shaped stem and a brown cap is the king bolete.

The king bolete sheet

Narrowed down

A bracket with pores, on wood.

Nothing in this group in the northern hemisphere will kill you, and several members are excellent. Chicken of the woods is bright orange and soft enough to dent; hen of the woods is a grey rosette at the foot of an oak. Turkey tail, reishi and chaga are here too and are not food: they are too tough to eat and are used as decoctions.

The medicinal ones, graded honestly

Narrowed down

Spines rather than gills: the tooth fungi.

A small group with no deadly members, which makes it the best group for a beginner to learn. Hedgehog mushrooms grow from soil and have soft cream spines that rub off with a thumb. Lion's mane hangs from hardwood as a white beard and is unmistakable.

The hedgehog sheet

High-risk group

Corals and clubs.

No deadly species, but several corals are strongly laxative and they are genuinely difficult to tell apart. Not a group to eat from casually. Cordyceps militaris is here too, as small orange clubs growing out of buried insect pupae.

High-risk group

Cup fungi.

A large group, mostly small, mostly not worth eating, and containing some seriously toxic members. Identification here usually needs a microscope. Enjoy photographing them.

Narrowed down

Flat wavy ribbons at a conifer base: cauliflower mushroom.

Distinctive, large, with no dangerous look-alike, and one of the small number of wild mushrooms genuinely worth learning first. The difficulty is entirely in the washing, because every fold holds conifer needles and grit.

The cauliflower sheet