 
TheGardenLady received this question from Ruth:
Is it true that fallen leaves can make good fertilizer? If the leaves can be used as fertilizer what are the benefits? Is it wise to mow/use as mulch the fallen leaves?
Fallen leaves make excellent fertilizer. This is nature’s way of making fertilizer without help from mankind; fallen leaves provide the nutrients that trees need and will enrich the soil – this includes increased soil organic matter, improved soil moisture holding, soil tilth (the physical condition of a soil), structure and fertility plus it helps the community dispose of leaves. See this link about recycling and mulching.
But the leaves left on a lawn or home garden have to be mulched unless you compost the leaves:Read The Garden Lady’s column Would You Throw Out Your Old Gold. It is very wise to mow your fallen leaves if you want to make the leaves into mulch and it is a lot easier than raking leaves. There are mulching lawn mowers or mulching attachments for lawn mowers the mulching easier. There are also mulchers – machines that you can buy to shred leaves. But you can use a regular mower, going over the leaves a few times to be sure the leaves are finely cut. It is easiest to mulch them by mowing them every few days so they don’t accumulate. You don’t want any more than 6 inches of leaf mulch. If the grass is visible after mowing, no other steps are necessary. If there are clumps of chopped leaves, either re-mow in the other direction to chop the leaves further, or rake them up and put them in your compostpile. And if you have too much mulched leaves for your lawn you can put them in your garden beds, flower beds and around trees and shrubs.