Leaf Litter Is Not Garbage

As deciduous trees prepare for the cold and dreary winter weather of the Northeast, they go dormant and shed their food-making factories, leaves. While many of us feel that this is a grueling time of year—keeping up with falling leaves in order to keep our park paths safe and our lawns from suffocating—we overlook the magic of leaves. Leaves are made of nutrients discarded from trees that are waiting to be recycled back to nature, not scrapped.

Under the cleanliness features of the Parks Inspection Program, leaves can be considered litter. However, PIP ratings standards have been modified so that leaves can be left in planting beds: “Natural debris will not be rated unacceptable unless it presents a safety hazard and is considered an Immediate Attention, i.e. leaves obscuring steps.” We all know that leaves are slippery, especially when wet, and even worse when covered with snow and ice. Leaves should be removed from all paved surfaces, synthetic turf and sandboxes.

However, in the world of horticulture, leaf litter is part of an important layer of dead plant material made up of leaves, bark, needles and twigs that have fallen to the ground. The term “soil food web” refers to the collection of micro-organisms in the soil that break down leaf litter and turn it into a rich, organic layer that supports life above and below the soil's surface. A healthy soil food web helps soil retain nutrients and fertilizers, increases water and air retention, improves soil structure, modifies pH, and can even break down toxins such as pesticides and heavy metals.

Soils are made up of 45% minerals that come from the parent material (bedrock or material deposited by wind, water or ice), 25% water, 25% air and only 5% organic matter. Soil organic matter consists of plant and animal residues in various stages of decomposition, and is the driving force behind the soil web; it can form naturally or can be made by composting. Only leaves that cannot be separated from garbage should be sent to landfills. All other leaves can be used to enhance the soil food web as decomposed organic matter.

Ideally, every park would have a compost bin, where leaves could be collected, mixed with carbon rich green material (grass cuttings, herbaceous weeds, and manure) and turned regularly to allow for good air circulation. The compost could then be used as an organic additive rich in nutrients and biological activity. However, managing a large compost pile is time consuming, requires heavy equipment, is hard to site, and can become unsightly. Small compost bins can be just as effective, and can be as simple as a chicken wire holding unit tucked into a mixed shrub and perennial border or a 10’ by 10’ fenced area outside of a playground.

Alternatively, leaves can be allowed to compost in place. Leaf litter acts as a natural mulch and can prevent erosion and suppress weeds. Sometimes leaves become too thick and threaten to smother lawns or perennials and groundcover and should be removed. Keep mulch mowing as late as possible into the fall until the leaves on the lawn become too thick and can no longer be shredded by the mower. At that point, consider relocating the leaves to wooded areas. Be sure to keep leaf litter away from plant stems and trunks to prevent crown rot. Remember that certain landscapes, such as alpine gardens, do not like rich organic matter high in nutrients.

Increased composting is a goal of Sustainable Parks. Leaf litter should be treated as a valuable resource and not a nuisance.

If you are interested in learning more about composting, please reach out to me at Central Forestry and Horticulture at crista.carmody@parks.nyc.gov or 718 760-6846.

Submitted by Crista Carmody

QUOTATION FOR THE DAY

“When we contemplate the whole globe as one great dewdrop, striped and dotted with continents and islands, flying through space with other stars all singing and shining together as one, the whole universe appears as an infinite storm of beauty.”

John Muir
Travels in Alaska, 1915

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