Stem

Central

When you ask a child to draw a mushroom, they always draw a cap with a stem right in the middle. This perfectly symmetrical shape, in which the stem is central (central stipe), is the most refined and most common architectural model in the world of macrofungi.

24 species in the database.

Why is the central stem so popular?

As David Arora explains, mushrooms that grow on flat forest litter or open ground (meadows, pastures) have no trouble orienting themselves in space. Their goal is to lift the cap as high and as level as possible so the spores fall straight down.

A central stem (like the pole in the middle of a tent) distributes the weight of a large cap perfectly, letting the mushroom grow straight up against gravity, even if its flesh is massive and full of water.

Classic examples

The vast majority of mushrooms that matter for cooking and toxicology have exactly this kind of central stem. As described by M.Ya. Zerova:

1. The bolete family (Boletaceae): Porcini, birch boletes, scaber stalks, slippery jacks. Their heavy, spongy caps are perfectly balanced on sturdy central stems.

2. The amanita family (Amanitaceae): Deadly poisonous death caps, panther caps and fly agarics always have a central stem. The symmetry of their build (central stem, perfectly round ring, evenly sloping cap margins) is often deceptive in its beauty.

3. Agaricus mushrooms (Agaricus): The familiar store-bought button mushroom is the very model of central symmetry.

4. Brittlegills (Russula): Always have a perfectly centered stem. Since brittlegill flesh is very fragile, any other (eccentric) stem position would make the cap break off under its own weight.

Questions and answers

Can a mushroom with a central stem grow out of a tree?

Yes! The best-known example is honey fungus (Armillaria mellea). Although it grows on stumps and tree trunks (where lateral stems often form), its stem is central. It manages this by growing in long clusters whose stems bend so as to bring the cap into a perfectly horizontal position, while the attachment to the cap stays exactly in the center.

If the stem is central, does that guarantee safety?

Unfortunately, no. How the stem is attached (central or lateral) has nothing to do with whether toxins are present. Both the most expensive truffles (if you count their pseudostems) and the most dangerous death caps grow with a central stem. Judge safety by the hymenophore, the volva and the ring!

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