We all have our sustainability buttons that get pushed. With me, it's seeing a strip of green grass between two curbs, a sprinkler watering the asphalt, and the water running down the street. For my friend Mitch it's seeing people raking leaves, putting them into plastic bags, and dragging them out to the curb.

"So what is it that bothers you about that?" I asked.

"Because it's stupid!" she said emphatically. "It's mining carbon. The leaves build soil, and when you throw them away you are throwing away the natural regeneration of the soil."

She pointed out that plants fix carbon out of the air, and then dead plant material when it settles on the ground builds tilth, which reduces run-off, improves infiltration, and increases the ability of the soil to hold moisture. Leaves and other plant material also add other nutrients besides carbon, and promote beneficial fungi.

She feels aggravated that people remove their leaves, and then have to add more water, and more fertilizer (which uses more petroleum resources,) to maintain their lawns. And the plastic leaf bags are made with petroleum, and gasoline is used to haul the leaves away. (In Moscow, the City invites you to drop off your leaves at the yard waste collection area at the recycling center. If you can't, you can schedule a pick-up for one of two named days in November. Latah Sanitation is composting and banking yard waste right now to have on hand to mix with nitrogenous waste—food scraps and possibly sewage treatment plant biosolids—in their new integrated composting facility. In Pullman, residents can rake their leaves into the street, where the city collects them and composts them at the cemetery, and the Parks department uses them as compost/mulch in city landscaping).

I looked up "leaf litter" in Edible Forest Gardens by David Jacke (Chelsea Green Publishing 2005). I learned that soil is composed of:

*The O layer, where all the organic debris collects and is broken down by myriad living decomposers;

*The A layer, where decomposed organic matter accumulates;

*The E or "effluvial" layer, where nutrients are leaching out;

*The B layer, where nutrients are banked;

*The C layer, where non-living chemical processes dominate; and

*The D (durable) layer, or bedrock.

I highly recommend this (two-volume) book to all gardeners. Jacke writes:

"...it is practically a cliché that healthy soil generates healthy plants...Less well known is the fact that plants are essential to the creation and maintenance of a healthy soil community."

"Many living things make their home in the O horizon...The usual human activities easily disturb these communities. They need time to develop their community structure, the right conditions, a diversity of organic matter foods, and may be a little tender loving care...When we eliminate the O horizon by tilling or raking up all the debris, we interrupt the processes by which nature builds the soil community and make the soil dependent upon our activities for its continued vitality. Such disruptions can also make the habitat inhospitable for the beneficial organisms, while encouraging the (organisms) we don't want. We humans must then work harder to keep things in balance, another example of shifting the burden to the intervener."

I asked Mitch what she would like to see people doing with their leaves. She noted that in my yard the leaves of the Norway maples lie where they fall, are still there in March as the carpet of violets begins to bloom, and by May have decomposed and "vanished." For those whose sense of art demands grass, she suggested that you can rake the leaves in a mulch ring around the trees, leaving a foot or so clear around the trunks, or you can rake them under shrubs, or you can collect them in simple wire composters and redistribute them to your yard as compost in the late spring.

Just take a leaf from nature, and leave those leaves!