I'm about to build a raised bed on top of a concreted floor. Part of
it shall be growing herbs and the other is for climbers and perenials.
It's about 20 foot long, 2 foot wide and 2 foot high.

In order to fill it, I've gravel for a couple of inches at the base,
then some dead branches I cut off a clematis last autumn which have
just been sat out in the rain and snow all winter, then I was going to
fill with topsoil. I do have a bit of cold compost (the grass
clippings and teabags kind!) but it's not really ready.

Would topsoil alone be sufficient? Does anyone know where I could buy
worms from?