Substrate

Living tree

If you see a mushroom growing not on a stump or a dead snag but straight from the trunk or branches of a living, green tree (one that keeps putting out leaves and growing), you're looking at a parasitic fungus.

The wood of a living tree is an extremely difficult substrate. A tree has a powerful immune system (resin, antiseptic compounds, thick bark) that protects it from fungi. So only very specialized species can use a living tree as a substrate.

24 species in the database.

How do they get in?

The spores of parasitic fungi can't break through healthy bark. They wait for an "open door" (a wound):

- Spots where the wind snapped off branches.

- Frost cracks (splits in the bark from hard frosts).

- Damage from insects (bark beetles) or animals (woodpeckers, moose).

- Wounds from careless pruning in the garden.

Once inside a wound, the spore germinates and the mycelium starts destroying the heartwood (the dead part) or the cambium (the living part) of the tree, causing different kinds of rot (white or brown rot).

The best-known mushrooms on living trees

1. Dryad's saddle (Cerioporus squamosus): A large, handsome, edible polypore with a mottled cap (and a cucumber smell) that very often settles on living walnut, maple and ash trees in parks. Its appearance means the tree's heartwood is already rotting and the tree may come down in a storm.

2. Honey fungus (Armillaria mellea): A jack of all trades. It can live as a saprotroph on dead stumps, but it often attacks living, weakened trees in the forest (or apple trees in the garden), hastening their death.

3. Beefsteak fungus (Fistulina hepatica): A blood-red mushroom that looks like a slab of raw meat. It grows mostly at the base of old, living oaks.

4. Chaga (Inonotus obliquus): A shapeless black growth (a tumor) that appears only on the trunks of living birches.

Questions and answers

If a mushroom has grown on an apple tree, can the tree be saved?

By the time the mushroom (the fruiting body) shows up on the outside, the mycelium has already been eating away at the tree from within for years. Cutting off the mushroom itself won't help the tree at all (it's like picking an apple — the apple tree doesn't disappear). The tree is doomed to a slow decline, but it may live and bear fruit for another 5-10 years.

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