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Alder

Alder — mushrooms with the trait «Alder»

Alder woods are dark, damp, often boggy patches of forest that many foragers never even peek into. And that's a mistake. The alder (Alnus) has an utterly unique mycorrhizal network and supports specialized mushroom species you can't find under any other tree.

1 species in the database.

Mycorrhiza and the alder's unique companions

In her "Key to the Fungi of Ukraine," M. Ya. Zerova points out that alder roots live in a double symbiosis: besides fungi (mycorrhiza), they carry nodules with bacteria that fix nitrogen from the air. This makes the soil under alders rich in nitrates, which shapes a very specific mycoflora.

In "Mushrooms Demystified," David Arora notes that the alder is an obligate partner for many highly specialized macromycetes. If you see these mushrooms, you can be sure alder roots are nearby:

1. Alder bolete (Gyrodon lividus): The best-known pored mushroom that grows only under alders. It has yellowish tubes that quickly turn blue when touched. It's a rare edible mushroom.

2. Paxillus rubicundus: A poisonous mushroom, the closest relative of the brown rollrim, but it forms mycorrhiza only in alder woods near water.

3. Alnicola: A whole genus of small, brown, inedible mushrooms that got their name precisely from their strict tie to the alder.

Roger Phillips also highlights the importance of dead alder wood. Fallen alder trunks rot quickly in a damp environment and are one of the best substrates for late-autumn and winter saprotrophs. In particular, the velvet shank (Flammulina velutipes) gives its biggest harvests on fallen alder and willow trunks.

For a forager, an alder wood is a place for targeted searching. Besides the specialized species, on the drier edges of alder stands you can come across brittlegills and milk caps that tolerate wet soils.

Questions and answers

Why do different mushrooms grow under alders than under oaks or pines?
It comes down to the chemistry of the soil. The nodule bacteria on alder roots enrich the soil with nitrogen. Many classic forest mushrooms avoid overly nitrogen-rich (nitrophilous) soils, while this environment is ideal for highly specialized species such as the alder bolete (Gyrodon lividus).
What is the alder bolete, and can you eat it?
The alder bolete (Gyrodon lividus) is a pored mushroom that forms mycorrhiza only with alders. It has pale yellow tubes and flesh that instantly turns blue when cut. The mushroom is considered edible after boiling, but it's fairly rare and is on protection lists in many countries.
Is it safe to pick velvet shanks on alder?
Yes, alder wood is an excellent and safe substrate for velvet shanks (Flammulina). However, always be careful not to confuse them with the dangerous funeral bell (Galerina marginata), which can also grow on the rotting wood of broadleaf trees.
Does chaga grow on alder?
Although the classic tree for chaga (Inonotus obliquus) is the birch, this parasitic fungus can occasionally attack alders too. However, the medicinal properties of "alder chaga" are considered weaker.

Sources

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