K wrote:
Jim Paterson writes

Leaves should be kept separate to be used as leafmould when ready. (
They rot down by fungal action as opposed to the composting process
which uses bacterial action) Having said that, a FEW leaves won't
hurt. hth

I've never really understood this. Why should tree leaves rot down any
differently from grass leaves or weed leaves or cabbage leaves?

Or is it that leaves in quantity settle into a soggy mass that isn't
aerated enough for the bacterial action?

I'm no expert on this, but I understand that deciduous trees put a lot of
nitrogenous waste into their leaves before they drop (this is a good way for
them to remove the excess nitrogen, and also helps to poison competing
plants which have the effrontery to try to grow around the tree). These
toxins take a long time to break down properly (that is the point in the
allelopathic poisoning of competitors), hence the longer decomposition time.