Autumn is the season of most obvious transition. Our part of the planet starts its annual wobble northward on its axis around the sun, and things cool down quickly. Days get noticeably shorter. Nature begins to enter its season of slumber.
For plants, the time of photosynthesis and fast growth comes to an end. Annual plants set their seeds in hopes of a new generation next spring. Deciduous trees can't make enough of the short days and the sun appearing low on the horizon, so nearly all of them shed their leaves. The sugars in the drying leaves convert into starches and are drawn back into the tree trunk as the tree enters dormancy. This causes the dramatic change in leaf colours and leads to leaves falling.
A healthy mature maple might drop 750kg of leaves. In a forest setting, these would form a natural mulch or leaf litter. This carpet of organic matter harbours a thriving metropolis of invertebrates and microorganisms, fungi and bacteria. And this makes very healthy soil.
In a garden or farm setting, this leaf drop is a treasured resource. It can be gathered and composted. It can be added as a top-dressing to raised beds. It can be heaped over lasagna gardens and no-dig gardens. And it can be dried for later use, as well.
We're lucky to have loads of deciduous trees in the hedgerows that surround our farm, so we do a bit of all of this. Rather than brown bag them for the city to remove, we store some of the bags in dry, unheated spaces over winter. By the time the compost pile is becoming active again in the spring, these stored leaves will have become some of the best "brown material" for compost layering.
It's a great luxury in the spring to have a store of completely dried tree leaves to add to soil mixes. The extra organic matter will improve porosity and water retention, and it will be loaded with beneficial soil bacteria.
And it's all free. If there is still time to save some autumn leaves, it is worth every bit of effort. Don't have a yard? Head to a park before they get hoovered up by the city. There is usually more than enough to go around.