Monday, March 8, 2010

Stem Butts

Have you ever gotten a mushroom at the grocery store and noticed that it had fine filaments on the bottom, sort of like roots? Many people think that mushrooms can be compared to plants, with a similar stem and a cap instead of leaves. The problem is, this is not the case. A mushroom is a fruiting body, and is more analogous to an apple on an apple tree than the whole tree. Also, mushrooms are very temporary features while the mycelium, the body of the mushroom, can live in the soil on inside logs for years or even decades. So when you have those root-like things attached to the bottom of a mushroom, it is actually a piece of the body of the mushroom, called mycelium. That part, along with the bottom half-inch to an inch of the stem is called the “stem butt” and carries some pretty powerful life force with it.

You see, a growing individual mushroom has certain cycles to its life, just like you and I. First of all, it tries to find the limits of its food. It will grow for weeks or years without fruiting to grab as much of the food source it is growing on as possible for itself. As soon as it reaches the limit of its food, or the boundary between itself and a competitor, it will stop growing and make some mushrooms. During this time, it puts all its energy into mushroom production. As soon as the mushrooms are spent, it begins growing again. The mycelium will look for more sources of food and will further seek to grow into and digest what it has claimed as its own. When it has enough energy stored up and the conditions are right, it ill make more mushrooms. When that is complete, it will leap off again into vigorous growth, on and on until the food is spent and the mycelium dies.

Perhaps you can see where I am going with this. The most vigorous growth in the life cycle of mycelium is right after it has finished producing mushrooms. When you have a fresh stem butt, you have a little piece of that vigorous growth that is ready to go. If you put that stem butt on a suitable growing medium, it can burst into life and be used to further propagate your mushrooms. My personal favorite is coffee grounds. I have used stem butts to make coffee ground spawn with a half dozen or so different kinds of mushrooms. I currently have a toilet paper roll growing with oyster mushrooms and all I did is put a stem butt down in the center. They also grow well onto wood sawdust to make sawdust spawn or wooden dowels to make plug spawn.

So next time you harvest fresh mushrooms, think about what you can do with the stem butts instead of tossing them in the compost. Or maybe the compost is a place they can really grow well!


  1. I never realized how easy it could be to grow mushrooms. Thanks for sharing this information!

  2. Which kinds of mushrooms have you had success with growing on coffee grounds?