Aardvark muttered:

This autumn, water the leaves in the bags to get them wet. Stick a
shovelful of earth in the top of each bag. Puncture holes in the bags
to let in air. Close the tops of the bags losely, just a twist will
do. Stack away and use as next winters mulch.

Just one wheelbarrow of last year's leaf mould sorted out a horrible bed of
sticky clay - I could literally *see* the stuff making the soil better -
it's magic, don't waste it.