Past their use by

This gorgeous thing, (a leek) is now only of use to look at.

They go from having an edible stem with layer upon layer of delicousness, to a solid woody stem that would break your teeth if you were crazy enough to try.

Where did all those wonderful layers go to? One moment it's one thing, and then, in no time, it's something else again.

How does that happen?

If your interested, look here for large.