Grow Mushrooms Canada ships freshly made mushroom kits and cultures that are grown under sterile conditions and are guaranteed to arrive free of mold or other contaminants. The white “stuff” in your kit is not mold, it’s the fungal mycelium which are growing on the the sawdust or wooden dowels in your kit. When provided the right conditions, this mycelium will produce delicious mushrooms. Mold is the bane of mushroom growing, as it thrives under the same warm humid conditions as mushrooms. Mold shows up as areas of black or green. If you see mold on your unopened mushroom kit or plug spawn contact us so we can replace it! Once you cut open your kit, it is exposed to mold spores that are always in the air. Over several weeks or months, the likelihood of mold invading your kit increases. To reduce this risk, keep the room as clean as possible, and run a hepa air purifier if you have one. If you are planning to expand your mushroom kit into pasteurized or sterilized substrate, use the contents immediately upon opening. Some people want to fruit their kit first, and then try expanding. While you can certainly do this, there is more risk of contamination since your kit will have been exposed to mold spores in the air. When inoculating logs with plug spawn, be sure to use clean hands and disinfect your drill bit to reduce any contaminants.