Self-growing mycelium insulation mats from wood chips for cold frame add-ons protecting winter greens

To create custom-fit insulation for your cold frame, begin by selecting a suitable mycelium strain and wood chip substrate. An aggressive, cold-tolerant wood-loving species like Pearl Oyster (Pleurotus ostreatus) is ideal for this purpose. Purchase grain spawn or sawdust spawn from a reputable supplier for a vigorous start. For the substrate, use hardwood chips, such as aspen, maple, or poplar, avoiding resinous softwoods like pine. The chips should be small to medium in size, not fine sawdust or large chunks, to provide the right balance of surface area and air pockets.

Before inoculation, you must pasteurize the wood chips to reduce competing molds and bacteria. Submerge the chips in a large pot or heat-resistant container and cover them with hot water, holding the temperature between 160-180°F for at least one hour. A cooler or insulated bucket works well for this. Afterward, drain the chips thoroughly on a clean screen or tarp until they are moist but not dripping water when squeezed.

Next, prepare a shallow mold that matches the dimensions of the cold frame area you wish to insulate, such as the north wall or a removable lid. A simple wooden frame lined with a sheet of plastic will suffice. Once the pasteurized wood chips have cooled to room temperature, mix them with the mycelium spawn in a clean tub or on a tarp. A spawn rate of about 5-10% by weight is effective. Break up the spawn thoroughly and distribute it evenly throughout the moist chips. Pack this mixture firmly into your prepared mold, ensuring good contact between the chips to encourage rapid colonization.

The incubation phase is critical. Cover the packed mold loosely with another sheet of plastic to maintain high humidity while allowing for some gas exchange. Place the mold in a dark, undisturbed location with a stable temperature, ideally between 65-75°F. Over the next two to four weeks, you will see white, web-like mycelium growing through and binding the wood chips together. The mat is fully colonized when it is a solid, white, and firm block that can be handled without falling apart.

Once fully colonized, the mat must be dried to halt its growth,