Answer:
A time when they're green. A time when they're brown. But both of these times, cause me to frown. But just in between, for a very short while. They're perfect and yellow. And cause me to smile.
The leaves are on the fruit, the fruit on the leaves. What is it?
It nukes food at the touch of a button.
Sauerkraut owes its existence to this head
What nut has a hole and is squishy?
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.