Buy Blue Oyster Mushroom Grain Spawn Online. Our pure mushroom grain spawn comes fully colonized and ready to expand. We grow the grain spawn in  6-lb filter patch bags. This oyster spawn is known for large fruiting bodies, fast spawn run, and a beautiful blue color that is vibrant when young. Buy Blue Oyster Mushroom Grain Spawn Online. It fruits at a wide range of temperatures and will fruit 3 or more flushes over the course of several months. Great to grow in alder chips, straw, supplemented sawdust, toilet paper, and many other substrates.