Using grass clippings as sun block for soil

Summer days are lawn days, with the hum of mowers in the neighborhood, the scent of grass newly cut, the sight of grounds cloaked in emerald velvet (or blotchy burlap if the owners are lax and the weather dry). For the environmentally minded, these are also days of lawn guilt. Even if we practice sustainable lawn care, eschewing weed-killers and chemical fertilizers, we wonder if these high-maintenance monocultures are justifiable and worth their care.

A large lawn is wasteful. That acreage would be better used to grow food, or native vegetation that sustains wildlife. But I’ve made my peace with keeping broad mown strips of grass between more diverse plantings at our place, as well as a few modest play spaces. We have grandchildren, after all. And there are ways in which lawn areas contribute to the well-being of our food gardens.

First of all, while our mown strips do make a pretty green frame for shrub beds and flower gardens, they also expose scurrying pest rodents such as crop-munching voles to predators such as hawks.

Second, lawns make a contribution to our garden’s fertility because their clippings are compostable. Yes, you can use a composting mower that chops up the clippings so that the lawn itself is fertilized. But if you rake the clippings up, those rich green mounds make great compost fodder, a nitrogen source that reappears weekly to help break down the dry-brown, high-carbon materials in the compost pile.

After the dead vines of spring peas are flung on the pile, we spread a layer of fresh grass clippings on top. After perennials are cut back in fall, we do the same.

And third, clippings make a handy mulch. In this case we let them dry out on the lawn after mowing, then collect them and spread a thin layer — at most an inch — on the vegetable plot as needed. Since they generate heat during decomposition if used green, it’s especially important to use them dry when mulching small, vulnerable seedlings. A very thick mulch of fresh, green grass clipping also will smell rank as it decomposes.

Unlike heavy mulches like shredded bark or hay, a grass mulch will not keep weeds from coming up, although it will deter some tiny ones. Its main role is to shade the soil surface from the sun. Even that thin layer will decrease evaporation, protect soil organisms, and decrease the need for watering. The weeds that do come up will be easier to pull. Think of a grass mulch as sunblock for the soil. It will also provide nutrients to the garden as it breaks down

Make a point of including clover in your grass seed mix. Some people consider lawn clover a weed, but it’s an attractive green one, and since it’s a legume it adds fertility to the lawn. (Nodules that form on clover’s roots help make atmospheric nitrogen available to plants.) So turn the lawn into a fertility machine for the garden, put up that volleyball net, and let the games begin.

Barbara Damrosch

Barbara Damrosch

Barbara Damrosch’s latest book is “The Four Season Gardener’s Cookbook.”

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