Answer:
I am a portal to another world which you cannot enter. Only you can see me but I can't see you.
Though not a plant I have leaves. though not a beast I have spine. Though many wouldn't need me I am more valuable than wine.
I am the thing that is used to make your weight. What am I?
I am flora not fauna. I am foliage not trees. I am shrubbery not grass.
I am used to bat with, yet I never get a hit. I am near a ball, yet never thrown. What am I?
It flows out of the soil, It burns you if it boils, And holds us in its coils, More valuable than gold, As black as it is old.