An Insult, or an Opportunity?

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By Adrian Higgins
Thursday, November 6, 2008

November is the month when nature's solar panels, leaves, detach themselves from their mother trees and shrubs, and fall to the ground. It's interesting to observe how people react to this phenomenon.

For some, each fallen leaf is an insult, every descent an act of wanton littering. By now, the neatniks are out there daily, gathering the leaves by rake or blower, bagging them or forming neat piles by the curb. One can only imagine their pain, having spent a weekend picking up each leaf, only to lie in bed listening to the wind undo all their work.

Then there are others who don't bother at all, and let leaves pile up through the winter. This is not good. Apart from the untidiness of it, matted leaves can kill grass and accumulate, harmfully, in the crown of plants.

I fall somewhere in the middle, picking up leaves on the lawn with the mower on weekends and pouring the mixture of leaf and grass clippings into a couple of compost piles. And when the garden beds are smothered in magnolia, oak and locust leaves, out comes the blower. I attend to this when I can, and if the garden floor is leafless by Christmas, I'm happy.

In this age of thrift and environmental concern, it seems bizarre that we then bag or curb our leaves to be taken away. And to where? Yard waste makes up 13 percent of our trash, according to the Environmental Protection Agency. Many municipalities divert this away from landfills and into composting yards, where the leaves are shredded and piled into steaming mounds that are halfway decayed come spring; enterprising gardeners then collect it and return it to their yards.

Wouldn't it make more sense, though, to keep the leaves on-site?

There are three ways of doing this (composting, creating a leaf mulch and making leaf mold), and you may have to employ all of them if you have a lot of old trees and the leaf drop is significant.

The importance of compost cannot be overstated. I got a behind-the-scenes look at two gardening institutions in the past year, Longwood Gardens in Kennett Square, Pa., and Prince Charles's garden at Highgrove in the English Cotswolds. In both places, the emphasis on compost production was paramount.

There is no better ingredient for soil improvement or for feeding the creatures of the soil that are so important for the well-being of our plants. But making compost scares a lot of people, who fear that piles will be unsightly, attract vermin and stink. All those concerns are real, and perfecting the art of compostmaking is difficult. But if you follow a few basics, you can avoid those pitfalls.

A compost pile should be large, about a cubic yard in volume, to create the critical mass for the decay organisms. It should be kept moist but not wet, and it should be turned occasionally with a pitchfork. The microbes that break down the pile need a mixture of carbon for energy and nitrogen for growth and generally a lot more of the brown carbon than the green nitrogen. Nitrogen can be found in such things as vegetative kitchen scraps, waste from the vegetable garden and grass clippings. Carbon can be found in such things as straw, wood chips and, yay, leaves.

Anything you can do to shred the ingredients first will speed their decay markedly. A pile that is balanced with brown and green material, kept evenly moist and turned will see the alchemy of 150-degree heat and rapid conversion into crumbly finished compost. But few compost piles in the real world attain that consistently, and the conversion simply takes a lot longer, as much as a year.

I have two bins, one an elaborate, four-sided, bottomless box of wood and metal mesh, the other a simple loop of chicken wire. I am not a big fan of tumbler bins because they're expensive and fill up quickly. Friends have enclosed bins of recycled plastic. They work well and keep out animals. They are fine for small urban gardens with moderate streams of green waste, but I'd need about 20 of them to handle the leaves in my yard.

In an open area in front of my bins, I assemble leaves into piles 12 inches high, six feet long and three feet across, and run the mulching mower over them back and forth. This converts them into shreds about the size of postage stamp. The pieces are scattered by the mower but are easily raked into a pile. They are used as the main brown material in both compost bins.

I pile the material high in the bins, knowing that the volume will halve as it decays. But the leaves keep coming, so I then rake the shreds and cart them to my flower and shrub beds. I use it as a mulch, laid two to three inches thick. The earthworms and other soil dwellers start the process of conversion, but this is a slow way to do it, and it takes a year for the litter to break down.

The third avenue is to pile the leaves in a place out of the way and let them break down into a material called leaf mold. This takes two years to turn into crumbly humus, at which point it can be used for seed starting or as a soil conditioner or potting mix. This is an option for people with large properties where the leaves can be stored in an inconspicuous corner.

Many compost experts, including Prince Charles's gardeners, make compost without tree leaves, which they use for leaf mold. This is because leaves slow the compost process and also reduce the nitrogen content of the finished product. I think it's something only purists need worry about. Compost made with leaves is still black gold for the gardener.


© 2008 The Washington Post Company

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