I'm like a sheltering tree
You planted in fertile ground:
When you carefully nurtured me,
My roots grew deeply bound.

I protected you from the rain
And life's many raging storms.
You delighted in me again
When days were sunny and warm.

My wood, it has no worth.
My fruit you cannot eat,
But above all things on Earth,
I am most precious and sweet.

There's one last thing to tell,
A hint from me to you:
You can't raise me by yourself -
I must be cultivated by two.

What am I?