pith?

[Derek Voigt]

So I hear when you are cutting a bowl blank from a log, you are to avoid the pith of the tree (pith being the center part of the tree).

Why?

[Harlan Coverdale]

The pith typically moves a lot as the wood dries. In many (most?) cases, logs begin to crack at the pith, then the cracks radiate outward from there. Removing the pith takes away one of the primary causes of cracking.

[Tony Wheeler]

you can just leave it if you just turn the pith out of it