I'm going to grow my spring onions in a planting bag: 100cm(l) x 40cm(w) x 27cm(h)
Is it deep enouggh?
What soil should I use? Can I use pure compost or should I mix it with sand?
This is the first time I've heard of them. But they look like a great idea for onions because of their shallow roots. Good luck with them. Please keep us posted as I'd like to follow your progress.