Plug Spawn are hardwood dowels inoculated with a specific type of mushroom, which are used for outdoor mushroom cultivation. They are easy to use, and produce outstanding results. They should only be used on freshly cut hardwood such as oak or maple, and it is best to find logs about 6 inches wide and 4 feet long. You are going to want to drill holes evenly around the log about 3 inches apart. The hole size is 5/16 inch, and the depth is 1 inch. After drilling the holes, simply hammer plugs spawn into each hole. Place the log in a shaded area without direct sunlight.