This study guide is an overview of some key CNG standards that most often trip up newer members and can serve as a helpful guide for non-mushroom producers who get the opportunity to conduct a CNG mushroom inspection. The primary focus is on our Mushrooms Standards, which are fully detailed here. Please direct any additional questions to the certification specialist at certification@naturallygrown.org.

Substrate

Substrate is the material that the mycelium grows in or colonizes.

Mushrooms are little sponges, so when selecting substrate, think naturally derived and low food safety risk. CNG producers most commonly use logs, sawdust, wood chips, straw (from wheat, barley, oats, and other non-GMO crops), and compressed sawdust blocks.

Most untreated wood products (logs, stumps, sawdust, chips) are ok, though logs must be harvested in a sustainable manner. Manure must be properly composted and derived from naturally fed animals. Coffee grounds are also allowed.

Substrates must be guaranteed non-GMO, so if the grower is using cottonseed hulls, cornmeal, or other byproducts of common GMO crops, these must be verified non-GMO. (It’s easiest and safest to just avoid crop residue that is commonly GMO).

Municipal compost (too many contaminants), fabric, paper, printed cardboard, treated or contaminated wood and any hint of GMO crop or residue are not allowed. In short, stay away from anything synthetic, potentially contaminated, or that contains unnatural additives.

Spawn

Spawn is material that has been inoculated with a specific mushroom strain, used to initiate mushroom production in the final substrate. Kind of like a seed!

Spawn can come in many forms, from bags of inoculated grain and sawdust, to inoculated wooden pegs, plugs, or compressed blocks and even in liquid form.

Since spawn is simply inoculated substrate, follow the substrate guidelines when sourcing spawn. Though it’s recommended that spawn be organic or CNG, it is not required, as long as the substrate is all good. Make sure to avoid glues or adhesives as well.

Caps

Caps, often made of some type of wax, are used to seal inoculated plugs into hardwood logs and stumps in outdoor mushroom production.

Wax should be food-grade, so beeswax, plant wax, cheese wax, and food-grade paraffin wax are all great. Avoid any perfumed, dyed, or painted wax. Polystyrene, petroleum jelly, and other synthetic products are not allowed.

Water Quality

Water is used in mushroom operations to soak logs and other substrate and to irrigate fruiting bodies.

CNG requires annual water testing for mushroom producers, at each water source. Though testing requirements vary by water source (municipal, well, surface, etc.), all sources must be tested at point of use for heavy metals or other potential contaminants common in the area for that water source. (Municipal water and well water is exempt if local experts say contaminants are unlikely in the area).

For producers using water to irrigate fruiting bodies (the mushrooms themselves or substrate that is in direct contact with the mushrooms) there are more stringent requirements, as there is increased food safety risk. Municipal and well water for irrigation fruiting bodies must be free from E. coli and surface water is prohibited.

In short, mushroom growers should ensure that they are in contact with the certification specialist regarding their annual water testing requirements. The mushroom inspection form has more details regarding how to determine a producer’s compliance regarding water testing.

Wild-crafted mushrooms

Wild-crafted mushrooms are fungi that are harvested in the wild, not cultivated by a producer.

This is an easy one—CNG does not certify wild mushrooms. So, if a grower is selling wild crafted and cultivated mushrooms, they can only label the cultivated mushrooms as CNG.