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The Dry Garden: Rake-and-bake compost made from fallen leaves

September 25, 2009 |  2:29 pm

While the urban forests of Southern California lack the autumnal glory of Eastern woodlands, fall happens here. We do have trees that shed. Moreover, the annual drop of their canopies by hackberries, sycamores and pecans (to name only a few) is still a bonanza. From these leaves, and just about any leaf that flutters to the ground, comes leaf mold.

What sounds like a disease is nothing more or less than compost made from rotting leaves. Handled right, leaf mold will condition the soil of garden beds and return important minerals such as calcium. It is the best sort of mulch, forming a protective covering that will cool the roots of plants while reducing evaporation and dust.

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Some trees mulch themselves. In the case of common semi-deciduous trees such as coast live oaks and avocados, the leaves drop so gradually, usually all the conscientious gardener need do is neglect them. That said, when dogs disappear into the mulch, the point has probably come to reduce but not remove the leaf carpet.

Meanwhile deciduous trees dump so many leaves at once every autumn that doing something with the leaves is an imperative.

Running the leaves under a mower then spreading them around less prolific shedders is a respectable tactic. But if you really have trees, and really have leaves, then you’d be well advised to compost.

To do this, also shred the leaves if you can. It’s not necessary, but it will speed up the composting. Then form a pile a decent distance from the house.

Next move: Water it occasionally. If decency allows, pee on it.

The urea will add nitrogen that will speed breakdown. (Autumn leaves are short on their own nitrogen because the trees that shed them withdrew their chlorophyll back into the root system before letting go.) As my brother quipped, using your own urea rather than buying it at home improvement stores will keep you under the radar of Homeland Security. It would even place you among the ranks of the funniest water conservation fraternity in the country: the Atlanta-based Pee Outside

However you wet the leaves, turn them as you add new loads.To speed up the composting in a more conventional fashion, add grass clippings. If you don’t have those, raid a neighbor’s green bin.

Better yet, since it’s pruning season, if you plan to have tree-trimmers through, request that they bring a grinding truck and leave you the pile of green mulch. This mix of freshly cut wood and leaves will be so full of nitrogen that the pile should start heating up even as the arborists are packing up their saws.

Tree trimmings will be ready to spread when they have cooled down and turned brown. The composting will not only have reduced the volume of leaves and twigs but will also have broken down them to the point that they will not wick water from soil. Rather, once composted, they act as a blanket conserving winter rains. 

Unlike store-bought mulch, this homemade sort will soon be jumping with life, chiefly earthworms.

Once worms appear, birds will follow. This will be music to your ears while you … pee outside?

-- Emily Green

Photo credit: Francine Orr / For The Times

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