The Enchanted Maze

The wooden well with the climbing roses has gotten the best of your curiosity. After stepping up to the well, the first thing you do is read its plaque:

A million miles I've traveled
and back.
A puzzler's mind is all I lack.
If you can solve this riddle from
afar,
a great puzzler indeed you are:

White as the snow
and high as a hills,
I am the one to cure
your ills.

I am not at all bitter,
in fact I'm very sweet.
But if you get too
much of me,
you won't think I'm
such a treat.