Minimum spacing for kale

I plant the black kale pretty close (30cm ish) as it has a tall vase shape which allows for this.  I find the curly stuff is a bit more bulky so needs more room, but I like the small leaves best anyway, so plant about 45cm apart and pick pretty hard to keep it compact and producing more of the new little leaves I like 

You can intercrop with something else until the kale grows a bit and needs all the space.  Salad leaves are my usual choice as they benefit from the netting as well and don't get demolished by the wood pigeons this way

Oh good, looks like I can get away with packing them in then

Thanks for that.

I only grow the dwarf green curled and put them no further than 12 inches apart. I've also grown them in containers and put two in a 12 inch square pot.

Close due to the amount of space and netting it can take up and still get a very good crop.