A New Use for old leaves Garden: Composting puts trees' leavings to good use.

November 01, 1998|By Ary Bruno | Ary Bruno,SPECIAL TO THE SUN

Overnight, it seems, the weather has turned chilly and brisk, and the trees are daily dropping their bounty of nuts for the squirrels to harvest. They are also dropping their leaves. This will shortly become a flood.

I am not fond of raking leaves, and because burning them is no longer permissible, I cannot even look forward to a bonfire. So what to do with them?

I am well aware that the municipalities around us provide leaf pickup days, but as a confirmed composter I always cringe at this waste of organic material.

Yet, leaves are notoriously difficult to turn into good compost or humus. However, there are ways to deal with them that even the most reluctant composter may adopt without too much effort. You may even find yourself, as I occasionally do, soliciting more bags of leaves from the neighbors once you get going.

If you are energetic about composting - the sort who turns the pile every few days for several weeks, inoculates it with "compost starter," checks its temperature daily to make sure it is cooking nicely at about 150 degrees, and so forth - you can have fine compost from leaves in about eight to 10 weeks. I plan to do this, too, when I retire.

The other extreme is to heap them up in a bin or pile indiscriminately and leave them there for two or three years, after which the ones on the inside will have broken down into beautiful leaf mold. This is a little longer than I want to look at a pile of leaves, however.

So now we come to the middle ground, where I firmly stand.

If you have a lawn mower, or can borrow one, it speeds things up considerably to run the mower over each low pile of leaves several times to shred them. The leaves can then be collected and put in a compost bin with other materials.

If you do not shred them, the leaves will take much longer to decompose. Unshredded leaves also have a despicable tendency to mat together into impervious layers. When matted they take a very, very long time to break down.

Compost piles are most often constructed in layers of material about 6 inches deep, one on top of the other. The goal is to get a good mix of carbon and nitrogen sources, plus some friendly microbes to get things "cooking."

Carbon sources are dried things, shredded leaves and straw being among the most common. Nitrogen sources are manure, dried blood, fruit and vegetable scraps from the kitchen, and fresh, green trimmings and wastes from the yard, such as grass clippings (do not use clippings that have been sprayed with pesticides, weedkillers, etc.).

Compost can be made in a simple pile, but most people prefer to use wooden or wire cages, or plastic bins made especially for composting.

Almost anything can be used to construct such a bin, such as hay bales, wooden shipping pallets wired together, or just a 4-foot circle of hardware cloth with a few stakes driven in to stabilize it.

The main idea is to make sure the pile is large enough to generate sufficient heat to break down the materials. Four-by-4-by-4 foot works very well, but a carefully constructed 3-by-3-by-3-foot pile in a bin will also do all right. Anything much smaller, though, you will have a hard time getting to heat up properly.

The more thoroughly things are mixed up together, and the smaller pieces they are in, the more quickly and completely they will break down into compost with the least additional effort on the gardener's part.

A mix that I have found to produce good compost is a ratio of three parts shredded leaves to one part fresh fruit and vegetable scraps or green yard waste, plus one part dirt or finished compost to introduce some friendly microbes to the pile. (The microbes are what do the main work of compost-making.)

Stable bedding from a farm or horse stable is also a great thing to add to shredded leaves in alternate layers. This is straw that has some horse (or other animal) manure mixed up in it, which provides nitrogen.

It is also helpful to throw in a couple pounds of dried blood and bone meal as you are making your leaf pile, scattering a handful or so on each layer.

Keeping a proper level of moisture in the pile will speed things along for you. The dampness of a wrung-out sponge is about right. It is also a good idea to cover your compost, both to help keep it warm and to prevent too much water from getting in and blocking the flow of oxygen through the pile.

If your pile does not heat up, it is probably too wet, too dry or needs more nitrogen. Check the moisture level first. Fluffing up the pile with a pitchfork and mixing in a bag of composted manure from the garden center will also help cure this, as will a few handfuls of dried blood thrown in while you mix it up.

If your compost-to-be develops a bad odor, it is usually short of carbon materials, or is undergoing anaerobic (oxygen-deprived) decomposition. To correct this, mix in some more shredded leaves, straw, etc., to adjust the carbon ratio and help balance the moisture level back to the damp-sponge stage. You can also mix in some lime to "sweeten" it.

Turning the pile will hasten the breakdown of the leaves. Turning introduces more oxygen into the compost. This in turn speeds up the rate of decomposition by generating more heat within the pile. The more quickly complete decomposition is achieved, the less nutrients are lost in gaseous form (ammonia) or leached out of the pile by the weather.

Even without regular turning, though, leaves treated in this way should produce fine compost for you to use by the spring. After all, nature's been doing it for thousands of years.

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