Key takeaways
- A substrate is what a fungus grows on and feeds from.
- Common cultivation substrates include logs, sawdust, straw, grain and nutrient media.
- Substrate affects yield, appearance and possibly composition.
- In mycelium products, the substrate may end up in the product.
Every mushroom grows on something. That “something” is called the substrate, and it matters both in nature and in cultivation.
Substrates in nature
Different fungi specialise in different food sources: Lion’s Mane and Reishi grow on hardwood; Oyster mushrooms on dead wood; chaga on living birch; Cordyceps on insects. See Parasitic and Wood-Decaying Fungi Explained.
Substrates in cultivation
- Hardwood logs: a traditional method, slow but close to nature.
- Hardwood sawdust, often supplemented with bran, packed into bags or blocks.
- Straw, especially for Oyster mushrooms.
- Grain, used to make spawn and, in some supplements, sold with the mycelium.
- Nutrient media, used for cultivated Cordyceps militaris.
- By-products, such as spent coffee grounds.
Why substrate matters
- It affects yield, growth rate and appearance.
- It can influence composition.
- In mycelium products, it may end up in what you buy. See Mycelium on Grain Explained.
Preparation
Substrates are usually pasteurised or sterilised before inoculation to prevent competing moulds and bacteria.
Substrates and sustainability
Fungi can turn by-products into food, and spent substrate can be composted. See Oyster Mushrooms and Sustainable Cultivation.