Someone please explain "birthing" mycelium for me

I understand the practice of cutting the bag off of the fully colonized substrate and the goal of exposing it to more oxygen in order to trigger fruiting. What I don't understand is why it is not always necessary.

In one of Stamets books, he describes the practice of column culture where the plastic collums, once filled with pasteurized straw, have x shaped holes cut into them every 4 inches so that the fruiting bodies have a place to emerge from. Since there is no "birthing" it seems to me that there is no change in O2 levels as part of the initiation strategy in this case.

I vaguely remember that the instructions for some mushroom kits also tell you to cut x-shaped holes anywhere you see primordia forming. Clearly there is no birthing or shift in air exchange to trigger fruiting in this case either.

So can someone explain to me what advantage is derived from "birthing" colonized substrate and how necessary it is?

Mycelium growth doesn't require a lot of oxygen. Fruiting requires more oxygen. If you have holes or x's, the pinned mycelium will send a mushroom toward that. Usually, a drop in temperature is required for pinning. This is also when it has run out of substrate, so it fruits, so the spores can go somewhere else and find a rich vein of substrate to decompose.
JohnS
PDX OR

John Saltveit wrote:Mycelium growth doesn't require a lot of oxygen. Fruiting requires more oxygen. If you have holes or x's, the pinned mycelium will send a mushroom toward that. Usually, a drop in temperature is required for pinning. This is also when it has run out of substrate, so it fruits, so the spores can go somewhere else and find a rich vein of substrate to decompose.
JohnS
PDX OR

So do you feel that since cutting X's in the bag is enough for primordia to form that birthing is necessary? Does exposing the entire substrate provide any advantages?

I am just learning to grow fungi myself, but since no one else has answered I'll try given what I've read and heard. I think on oysters and others that are reasonably easy to grow, yes, an x is enough. On the extreme fungi sites, they go on for hours about pinning strategy, etc. For difficult mushrooms, I can't really tell you. I'm going to stick to the easy stuff until I at least get good at that.
John S
PDX OR