How to Take a Spore Print — and Why It Matters So Much

The spore print is the highest-value thing an amateur can do, and almost nobody does it. It costs nothing, requires no equipment, and it settles two of the confusions that kill people.

How to do it

1. Cut the cap from the stem with a knife, as close to the cap as you can.
2. Place it gills down on a sheet of paper. Use paper that is half white and half black — a white print is invisible on white paper and a black one is invisible on black.
3. Cover it with a bowl, glass or cup. This stops draughts blowing the spores away, which is the usual reason a print fails.
4. Leave it several hours, or overnight.
5. Lift the cap straight up and look at the deposit. Judge the colour where it is thickest.

If nothing appears, the mushroom is either too young to be dropping spores or too old to have any left. Try another specimen.

What the colours mean

The two prints that save lives

White versus rusty brown, on wood. Honey fungus and the deadly Galerina both grow in clusters on dead wood, both are brownish, both have a ring, and both appear in autumn. Honey fungus is widely eaten. Galerina contains the same amatoxins as the death cap.

Honey fungus prints white. Galerina prints rusty brown. That is the whole difference, and it has killed people who did not check.

White versus brown, in grass. Field mushrooms and destroying angels can both be white mushrooms in grass. Field mushroom gills go pink then chocolate brown and the print is brown. Destroying angel gills stay white forever and the print is white.

Gills that stay white on a white mushroom in grass should stop you every time.

What a print does not do

It gives you a genus-level clue, not a species. A white print is shared by chanterelles, oyster mushrooms, russulas and the death cap — an enormous range of consequences.

So the print narrows; it does not conclude. Combine it with:

• What is under the cap — gills, ridges, pores or teeth
• The stem base, dug up rather than pulled, checked for a cup
• A ring on the stem
• The substrate — wood, soil, grass or dung

The habit worth building

Take a print of everything you find, even things you are not remotely considering eating. It costs nothing but a bowl and a night, and after a season of doing it you will have an intuition for which genus you are looking at that no amount of photograph-matching produces.

And when the print does not match what you expected, that is the print doing its job.

Reading a print that came out badly

Prints fail in a small number of ways, and each has a fix:

A cap that is genuinely too old will have dropped most of its spores already, often leaving a visible dusting on whatever is beneath it in the field — which is itself a usable print if you notice it before picking.

Keep the prints

A print on paper keeps indefinitely if it stays dry. Writing the date, the substrate and where it was found on the same sheet turns a season of walks into a reference collection that is worth more than any book, because it is local to you.

Use it alongside the identification key rather than instead of it.