Your Valuable Leaf Crop - Don’t Waste the Fertilizer Value

Both home gardeners and commercial growers are bothered and blessed by the problem of what to do with leaves, vegetable waste and crop residues. Rightly handled, this material is not an unwanted waste but a valuable byproduct.

Right at the beginning it should be said that burning (as what use to be common practice) is rarely the best method of leaf and surplus vegetable disposal and the semi-annual smogs of fall and spring clean-up campaigns indicate poor management of and a loss of valuable fertilizer material. In fact, it is not unusual to burn up tree leaves and garden residue and a few weeks or months later, spend real “folding money” for commercial fertilizer or a truck load of “black dirt” with no more soil improvement value than the leaves so thoughtlessly consigned to the flames.

About the only exception is leaves infected with some serious disease, which is relatively rare, or those like walnut and eucalyptus which are believed to contain substances toxic to some plants. Even in the latter case, it is possible that several months of weathering or composting will eliminate the objectionable factors.

As trees root more deeply than most annuals and other herbaceous plants, they bring up and store in their leaves minerals found deep in the sub-soil. Biological chemists have made analysis of tree leaves and have published tables showing the mineral content and fertilizer value of different species. These are too long and elaborate to be of interest to anyone not a plant food specialist, but they contain some conclusions of value to home gardeners, Tree leaves contain calcium, magnesium, potassium, phosphorus and nitrogen, with basswood ranking exceptionally high in mineral content.

The sugar maple also ranks high, not only for the quantity of its leaf crop but for its fertilizer value.

Leaves are not only a source of minerals from deep in the soil but also a source of humus, the activator of the soil. Humus retains moisture, loosens and aerates the soil, improves drainage, feeds the bacteria which break down the soil wastes into plant foods and itself releases plant foods slowly. We cannot long continue to rob the soil bank without making some new deposits and not use up our capital, its fertility.

Our biggest problem each fall is the proper disposal of the multitudes of leaves. Here we have two approaches, either pick up the leaves or dispose of them in place. Let us begin with the latter.

Leave Them on the Ground!

Direct, on-the-ground leaf grinding is made possible by the use of many rotary lawn mowers equipped with suitable attachments. Their outstanding advantage is that they can reduce the cut herbage to a finer consistency than other types of mowers. The machines operate on a suction principle. The leaves are drawn into the machine and cut to bits by the rapidly revolving blades. This finely-shredded material falls to the ground as a beneficial mulch, returning to the soil those nutrients which were taken from it. Likewise, the material is quickly incorporated into the soil, while it might take as much as two years for the whole leaves to decompose and the lawn grass beneath would be killed off in the process as well.

The other alternative, raking, is slow. Ordinary garden rakes are too small and the teeth too short. They fill up quickly. Also, one must do a lot of arm and leg work to clear a small space even when using a leaf tarp to gather the leaves. The modern rubber, plastic or wire rakes (yard brooms) are much faster than the old wooden rakes of yesteryear. However, there are several rotary brush lawn and leaf sweepers available at a price moderate enough to justify their use on relatively small lawns and gardens. One with which I am familiar weighs but 15 pounds, has a canvas catcher which holds three bushels and operates at better than three times the speed of ordinary hand raking with little effort.

For large scale lawn sweeping and leaf gathering there are also machines that operates like a vacuum cleaner. For some years municipalities used large suction leaf gatherers for collecting street-side leaves. Now, however, the use of a backpack leaf blower that is more flexible and less expensive and a whole lot m ore fun than hand raking or driving machinery around.

Once the leaves are raked or picked up mechanically, there is the problem of how to haul them away. One of the simplest ways is to rake or dump the leaves on a large canvas square (leaf tarps) or piece of plastic sheeting available from many of the larger garden centers. When it is full it is picked up by the handles or tied corners and carried or pulled away.

Of course, all that we have said about the value of saving leaves also applies to grass clippings. A serious mistake is the discarding of these clippings, for this short-cut grass which British dairymen call “high-protein grass” is of more value as a soil improvement ingredient than more mature plants or stalk residue. But these clippings are often swept up and taken from the lawn where they were grown, dumped or sent off in a garbage truck. So it is that such organic materials, potentially rich in soil improvement value, are lost.

Now that we have the leaves and plant wastes all picked up, what do we do next? First, they can be applied as a fairly heavy mulch to such plants as camellias, rhododendrons, azaleas and other plants that require an acid soil, for without a little lime such materials are often acid. Such a use is good. Secondly, we can mix the leaves and clippings into the soil, but unless incorporated thoroughly into the soil many leaves have a tendency to mat and remain undecayed for several years. That is not good.

Thirdly, the material can be chopped up in one of the leaf shredders or grinders now readily available from manufacturers like Patriot, WorX, Flowtron, McCulloch, Troy-Bilt, Toro, Yard Machines, Ariens and restored to the soil as a mulch, incorporated into the soil or built into a compost pile. The machines available for this purpose use to be too large and costly for homeowners and smaller commercial companies. Now, however, there are a number of them which serve the purpose admirably.

These are table or wheel-mounted machines, powered by electric motors, gas engines or belt driven by garden tractors. The price range of these machines is within the budget of ordinary garden owners. An electric leaf shredder sells for around $150. A larger capacity machine like a gas powered Patriot or Yard Machines model is priced somewhat higher ($500 - $900) but has a much higher per hour capacity. It all depends upon which best meets the particular need and pocketbook.

There are also some instances where bagged autumn leaves are a serviceable garden adjunct - a source of mulching material for next year - but it is a time-wasting operation to try to hold bags open with one hand and stuff it with the other. The best way is to make a bag-holding frame to keep the bag open.

Bagged leaves, however, should not be stored in buildings. They are a fire risk and make a home for rats, mice and insects. Store them in a corner of the garden. The bags depending on the type may retain their tensile strength through one winter’s exposure.

Another good over-winter leaf storage container can be made of poultry wire. This should be about 4 feet high. A 1-inch mesh holds the leaves better than 2-inch. By such storage one can keep a supply of mulching material for keeping down the weeds and retaining moisture in the soil on next year’s vegetable crops and berry bushes. And my own experience shows that many more gardeners need to know more about the advantages of mulching contrasted with weed pulling and ground cultivation, as well as the value of saving humus-building materials.

by A Whallon

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