Question related to Gro-Bags
 

Hi,
Does anybody know what's in a gro-bag? I used to see these things some
years ago in the UK but they don't seem to be available here in France. I
want to grow tomatoes on my balcony - what should I grow them in? Would a
bag of compost slit down the back do the trick or should I add something to
the compost?
Thanks in advance
Clive