I have always heard that leaving a few leaves on the lawn is a good thing. But when I visited the New York Botanical Garden recently I saw pristine lawns with no leaves in sight. So which is better?
I asked Kurt Morrell, who is the NYBG’s head of landscape operations. It turns out he is passionate on the topic of leaves because it has become a hot-button topic for municipalities around the country. Recent university studies have looked at the issue of "yard waste management" because of the negative impact on the environment of large piles of leaves and grass clippings in municipal landfills.
At the NYBG, Kurt uses a mulching mower for the lawns early in the fall, so that the leaves get chopped up finely and left right on the grass. They are invisible to the eye, especially from a distance. Later in the fall, when the leaf drop is heavier, instead of mulching them he picks them up and transports them to the compost heap. The NYBG produces 1,500 yards of compost a year and leaves are an important component of the mix. The following spring that compost is used in a variety of ways in garden beds and tree wells.
Are chopped up leaves bad for your lawn? Many home owners (including myself) wonder whether there are long-term negative effects of leaving leaf mulch on the lawn. The recent university studies, conducted over several years, have enough data to show that there are no negatives, and in fact there are some positives. What they found is that overall soil quality improves, with no substantial buildup of leaf mat, regardless of what types of trees you have (needled pines excepted). The increase in microbial activity breaks down the chopped up leaves and improves aeration, water infiltration and even weed management. The key is to chop up the leaves finely with a mulching mower.
Is Doing Nothing an Option? I like the look of a clean lawn, so it wouldn’t occur to me to leave my lawn full of leaves. That’s a good thing, because turfgrass specialists told me unshredded tree leaves can smother the grass and kill a lawn. Even a thin layer can rob your lawn of access to the sun and increase the chances of snow mold in the winter.
Leaf Shredder One of my horticulturist friends, Ruth Rogers Clausen, loves her leaf shredder. She throws armfuls of leaves down the shoot and into a kangaroo bag, then layers them on her garden beds for the winter. In the spring she takes a pitchfork and pokes it into the top two to three inches of her garden beds, gives it a twist and fluffs up her soil.
Leaves for Compost Pound-for-pound, leaves have twice as many minerals as manure, according to the plant specialist at the New York Botanical Garden who answers a consumer call-in line. Leaves provide much needed carbon, which complements the nitrogen found in grass clippings and other compost greens. If you can shred the leaves first they will decompose faster.
Dorian Winslow is the president of Womanswork, and is passionate about making the best products on the market for women who garden and work outdoors.
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