Mycelium

Mycelium is the main body of a fungus: a branching web of microscopic threads called hyphae that grows through soil, wood, leaves or grain. It absorbs water and nutrients from its surroundings and, when conditions are right, produces the visible mushrooms we call fruiting bodies.

How big can mycelium get?

A single mycelial network can be astonishingly large. A honey mushroom (Armillaria) colony in Oregon's Blue Mountains spreads across roughly 2,000 acres and is often called one of the largest living organisms on Earth. Most mycelium, of course, is far smaller and hidden in a patch of soil or a single log.

What mycelium does in nature

• Decomposition: It breaks down dead wood and leaves, returning nutrients to the soil.
• Partnerships: Many species form mycorrhizal relationships with tree roots, trading minerals for sugars. These links are sometimes nicknamed the "wood wide web."
• Soil structure: The threads help bind soil particles together.

Mycelium in products

Mycelium is also used commercially, from meat alternatives and packaging materials to leather-like textiles. In the functional mushroom market, some ingredients are made from mycelium grown on sterilized grain, often labeled "mycelium on grain" or "myceliated grain." Because the grain is not fully separated, the finished powder can contain a meaningful amount of starch. Other products use only fruiting bodies, or a mix of both. Some compounds are found mainly in one part; lion's mane, for example, has compounds researched in its mycelium that differ from those in its fruiting body.

Shopping tip

If a label says "mushroom," check whether it means the fruiting body, the mycelium or both. Brands that name the species, the part used and their extraction method make comparison much easier. It is the same kind of transparency that helps you spot genuine products; our guide on how to spot authentic Polkadot chocolate bars covers packaging details worth checking.