Should You Refrigerate Mushroom Spores?

Mushroom Spore Substrates

• Mycelium is usually transferred to other materials to grow mushrooms. Cardboard, straw, logs, sawdust, compost and wood chips are a few examples of growth mediums called substrates. Substrates are not necessary to grow mushrooms, but a small quantity of spore will impregnate a hefty amount of substrate, thus creating many more mushrooms than spores or spawn alone. Spent mushroom substrate is the compost left over from growing mushrooms that contain remnants of beneficial mycelium for other plant growth.

Spore and Spawn Shelf Life

• Mushroom spores and spawn deteriorate quickly, rarely lasting two months even in cold storage. Purchased spawn will have the inoculation date on the container. Use spores as soon as possible to prevent ruin. Yellow spots in the spore bag indicate mycelium waste accumulating due to bacteria, mold or other contaminates. Time is a precious commodity in mushroom production, so if immediately using spawn is not feasible, quickly prolong its lifespan by refrigeration.

Preventing Contaminants

• Mushroom spores and spawn are conveniently sold separately or in kits, from stores or online. Purchased bad-quality spawn spores have excessive brown liquid floating in the bag and should not be used for substrate inoculation. After buying, do not open the container until right before use to prevent stray fungal contaminants from floating around in the air. Research for highly recommended spawn producers pays off, as quality widely varies among numerous vendors.

Cold Storage Guidelines

• Preserving mushroom spores for future use is straightforward. Keep refrigerated spawn and spores between 34 and 40 degrees Fahrenheit. Spawn grown on sawdust or grain substrates can survive in cold storage for up to three months. To encourage vigorous fungal growth, store spores and spawn in a dark place at 70 degrees F three to 10 days before substrate inoculation. Mushroom spores and spawn should never be frozen, so keep a close watch on the refrigerator's internal temperature.