How to take a spore print and why it matters for identification

The short answer

A spore print is the dust of spores a mushroom cap drops onto paper. To take one: cut the stem off a fresh, mature cap, lay the cap gills-down on paper that is half white and half black, cover it with a bowl, and leave it for at least two hours, longer if the cap is old. The colour of the print tells you which family the mushroom belongs to. It matters for safety because the deadly death cap and destroying angels drop white spores, and the deadly funeral bell drops brown ones, while the edible mushrooms they are mistaken for often do not. The print is a clue to identification, not an edibility test, and it is something you do at home, not something an app does for you.

What you need

A mature mushroom with its gills showing, a piece of white card and a piece of black card (or one sheet half and half), a bowl or glass big enough to cover the cap, a knife, and optionally hair spray or artist's fixative to preserve the print. The British Mycological Society's primary-school resource lists exactly this: a mushroom, white/black card, a bowl, and hair spray.

How to take a spore print

1. 1. Pick a mature cap. A cap that has opened and shows its gills, pores or spines. Buttons and eggs drop few spores. If you are identifying a find, take the print from the same mushroom you photographed, and keep each species separate.
2. 2. Cut off the stem. First Nature recommends cutting with a sharp knife unless it snaps cleanly, so the gills can sit flat on the paper.
3. 3. Lay the cap gills-down on the paper. Place it across the join between black and white so the print lands on both. The BMS says there is no need to press it down. Michigan State's bulletin advises white or black paper because "colored paper can give a distorted impression".
4. 4. Cover it with a bowl. The cover stops the cap drying out and stops air currents blowing the spores about. For a small cap that dries fast, First Nature suggests a piece of wet tissue on top of the cap.
5. 5. Wait. At least two hours for a freshly picked cap (BMS); First Nature allows two or three hours under a tumbler. Leave shop-bought or dry caps overnight.
6. 6. Lift the bowl and the cap straight up. You should see a pattern of radiating lines matching the gills. Read the colour in daylight against both the white and the black halves.
7. 7. Fix it if you want to keep it. A light mist of hair spray (BMS) or artist's clear varnish (First Nature) stops it smudging.

Boletes, hedgehog mushrooms and other non-gilled fungi print the same way and leave a dot or ring pattern rather than lines. Cup fungi go fertile-side down. No print after a night usually means the cap was immature, dried out or already spent.

Reading the colour

Spore colour is one of the fastest ways to place a mushroom. First Nature calls it "one of the best ways of determining which mycological family the specimen belongs to". Field guides sort gilled mushrooms by it, which is why the print often decides between two look-alikes faster than any other feature.

Why spore colour matters for safety

Three of the worst mistakes foragers make are decided by a print.

White print, ring, sac: Amanita. The death cap has a white spore print, as does the destroying angel, and both carry a ring and a sac at the base. The field mushroom that white Amanitas are mistaken for drops a dark brown print, and First Nature notes its gills start pink and turn brown, unlike the pure white gills of a destroying angel. A white print from a mushroom you took for an Agaricus should stop you cold. See meadow mushroom vs destroying angel.

Brown print on wood: check for Galerina. The funeral bell, or deadly galerina, has a snuff-brown print and contains the same amatoxins as the death cap. Honey fungus, which grows in the same clusters on the same stumps, has a white print. Michigan State's bulletin puts the rule plainly: Galerina yields brown spore prints. The honey fungus vs deadly galerina page walks through it.

Green print in the lawn: green-spored parasol. The big white lawn mushroom that poisons more North Americans than any other drops a dull grayish green print, while the edible parasols it resembles drop white. Young specimens have white gills, so the print is often the only early tell. See parasol vs false parasol.

Common mistakes

• Reading a thin print as white. A faint print looks pale on any paper. Give it more time and check both halves.
• Trusting the gill colour instead. Gills and spores can differ; Michigan State notes the green-spored parasol's gills turn pale green only in maturity.
• Mixing specimens. Two caps from different patches on one sheet give one meaningless answer.
• Printing a cap that is too young or too old. No spores either way.
• Eating on the strength of a print. A print never clears a mushroom.

Spore prints and identification apps

Mycoscout does not take or read spore prints, and no photograph can. What the app does is work from the four field photos, cap, gills, stem base and habitat, lead with the edibility verdict and name the dangerous look-alikes to rule out. Its result names a species; look up that species' spore colour and compare it with your print. A white print where a brown one was expected means the match is wrong, and you know it before you go any further. Treat the print as your check on the app, never the other way round, and never eat a wild mushroom on the strength of either. How Mycoscout works.

Frequently asked questions