Cap surface

Slimy

A slimy, sticky or gelatinous (viscid, glutinous) cap surface is one of the most striking — and, frankly, messiest — features in the forest. Pick up a mushroom like this and your fingers turn sticky and are hard to wash clean with water.

This slime isn't a "byproduct" — it's a powerful evolutionary tool. As David Arora points out, the slime (made mostly of polysaccharides) does two jobs:

1. Holding on to water: The thick slime works as waterproofing. In dry weather it hardens into a tough crust that keeps moisture from evaporating out of the flesh.

2. Protection from being eaten: Most slugs and insects find it extremely hard to chew through a thick layer of gel, which clogs up their jaws. Often the slime also tastes bitter.

24 species in the database.

The kings of slime

Roger Phillips and M.Ya. Zerova single out several groups of mushrooms for which slime is a defining species trait:

1. Slippery jacks (Suillus): The forest's top "slugs". The slippery jack and the larch bolete have caps generously coated in a thick layer of sticky brown or yellow slime. Pine needles, sand and leaves get stuck fast to these caps.

2. Spikes (Gomphidius): For example, the slimy spike. This gilled mushroom isn't just slimy — it looks as if it's been dunked whole into a jar of runny, clear gelatin. Even the ring on its stem is slimy.

3. Roundheads (Stropharia): The poisonous or inedible verdigris agaric has a strikingly beautiful but very slimy emerald-green cap.

In the kitchen

The main rule for handling slimy mushrooms: the slime has to go.

On slippery jacks the slimy skin peels off easily from the edge toward the center of the cap. If you skip this:

- Your soup or marinade will turn into a thick, unpleasant, jelly-like mass.

- Slippery jack slime contains substances that act as a strong laxative and cause stomach upset in many people.

Questions and answers

How do you tell a slimy mushroom from a smooth one that's just wet from rain?

After rain, every mushroom is wet. But water on a smooth brittlegill is simply wet (like on glass). The slime on a slippery jack swells in the rain — touch it and long, thick, sticky gelatinous "threads" will stretch after your finger.

Are there slimy amanitas?

Amanitas are usually dry or slightly sticky. In damp weather, though, the death cap can have a faintly tacky (but not gelatinous-slimy!) cap. Real thick slime is mostly typical of boletes (slippery jacks) and certain gilled species (spikes, woodwaxes).

Sources

1.Зерова М.Я. та ін. Визначник грибів України. 1979
2.Roger Phillips. Mushrooms (Roger Phillips)
3.David Arora. Mushrooms Demystified
4.Index Fungorum