Making the Best of the Fall
Though many of us probably wish it were otherwise, summer has ended and it is now officially autumn. Though the warmth may yet linger awhile, before we know it, the leaves will be falling, and, if you expend a tiny amount of effort, those leaves will provide a useful addition to your garden: leaf mold. Despite the unpleasant name, leaf mold is just the name for the fibrous organic soil conditioner created as leaves break down. Since trees have roots that extend deep into the soil, they are able to absorb useful minerals that other plants cannot. Some of these minerals end up in the tree's leaves and allow those leaves to break down into a useful product.
Leaf mold has a multitude of potential benefits, including improving the structure of soil and making conditions ideal for beneficial soil organisms. It betters the structure of any type of soil, whether helping aerate heavy clay soils, preventing sandy soils from drying out too quickly, or just soaking up rain and preventing evaporation. It is a renewable resource, unlike peat, which is often used for the same purposes, and it is free, unlike chemical fertilizers and soil additives. Leaf mold can retain up to 500 times its weight in water, so it is very useful in keeping your plants moist during times of drought. It helps plants get the nutrients they need by bringing down soil density to allow the roots to penetrate deeper into the ground where these nutrients lie. It also helps repress weed growth, is useful as a component of potting soil mixes, and can be used as a winter cover to protect new seeds and the garden bed from harsh winter weather extremes. If your lawn needs the benefits more than your garden (or you don't have a garden), you can also just use a mulching mower to shred the leaves where they fall and leave them to decompose directly on the lawn.
Making leaf mold is simple: collect leaves; allow them to decay. It does take a lot of leaves to produce a substantial amount of leaf mold, but your neighbors probably wouldn't mind you taking some off their hands if you want extra, especially if you'll collect them yourself. Better you put them to good use than have the city pay someone to collect them and use them elsewhere! Do be wary, however, of leaves from lawns that have been sprayed recently with chemical pesticides or herbicides and leaves that have been near the street, as these may have collected fuel and oil residues that may harm your garden. Some trees' leaves are less suitable for making leaf mold than others, like black walnut leaves, which may be toxic to some of your plants, but the majority are acceptable. Leaves take a long time to decompose, between 1 and 2 years, but considering the amount of work involved (very little!) and the amount some people pay to purchase what you can get for free, it's worth it. And, if you exert a little effort, you can speed the process so that you might even have something usable by the next growing season.
The simplest method is to collect the leaves, place them in a pile somewhere inconspicuous, and leave for two years. However, you will be better off if you make some sort of cage-like container for them, so they don't blow away. An alternative to building or purchasing a cage is to put the leaves in a plastic garbage bag (or multiple bags) and poke a few small holes in the bag to allow air and water to pass through. To speed along the process in either case, try chopping/shredding the leaves with a lawnmower. The smaller the pieces, the faster the decomposition will be. Allowing your pile to be in contact with the ground may help speed the process, as soil organisms already in your soil may find their way up into the pile to help it decompose. Also, make sure that the leaves are moist (but not soaking wet). Another possible way to speed up the process is to include a small amount of grass clippings or green weeds to add nitrogen to the pile and turn the pile every few weeks. If you have chosen to make a pile rather than using bags, cover the pile with a plastic sheet to keep in warmth and keep moisture in and out. This will also keep the leaves from blowing away, provided you sufficiently weigh down the tarp. Thus, with a little bit of work and a fair amount of patience, you can have a free soil improvement for your lawn or garden.