What Do The Dark Cores In Trees Mean?

Q: Why do many tree trunks and limbs have a dark core in the middle? 

A: As a tree gets older, the wood tissue of the trunk and limbs divide into two zones: heartwood and sapwood. Heartwood cells usually contain tannins or other substances that make it dark-colored and sometimes aromatic. Heartwood is resistant to decay; often it’s the only thing left when a pine trunk is left to decompose. This “fatwood” is saturated with resin and is great for fire starting. Sapwood is lighter in color. This sapwood is where water and dissolved minerals are transported between the roots and the crown of the tree and, to a lesser extent, where excess food is stored.