Why are some of my mushrooms growing on the side?Updated a year ago

Side pinning usually occurs when oxygen inside the bag comes into contact with the side of the growing medium. Oxygen is a necessary part of the growing process and signals to the mycelium to fruit in specific areas. 

To prevent side pinning, a rubber band can be placed around the middle of the growing medium on the outside of the bag. We recommend a snug fit. Just enough to keep the bag on the side of the growing medium up against each other. Doing so will limit the amount of oxygen exposure coming in contact with the sides of the growing medium. 

If your bag has already begun to show signs of side pinning. Then a rubber may be placed to reduce additional mushrooms from fruiting on the side. Any mushrooms present below the rubber band will cease growth. 

So it’s important to place the rubber band after the growing medium is fully colonized and before pinning.