Grass clippings add nutrition to the lawn as they break down and so usually don’t need to be bagged or removed – if you’re cutting often enough that lawn-smothering mats of clippings aren’t being left behind. But on occasions when the clippings build up to the point where they need to come off, one good place to use them is as mulch in the vegetable garden.

Grass clippings are high in nitrogen – an important fertilizer that most plants need in regular amounts. Clippings also have a variety of other nutrients that they return to the soil as they break down. In the short term, a layer of grass clippings also acts as a mulch, cooling the soil, slowing the loss of moisture, and holding down the germination of new weeds.

Grass clippings in wheelbarrow
When used correctly, grass clippings can serve as a great mulch for your vegetable garden.
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Three caveats

While grass clippings are a good thing in the vegetable garden, consider three caveats before dumping them indiscriminately:

  1. Has the lawn been treated recently by an herbicide (i.e. weed-killer)? Herbicide residue can be carried on clippings into the vegetable garden, where it’s possible the herbicide could harm or kill vegetable plants. It’s best to use grass clippings only from untreated lawns… or if the lawn has been treated, wait at least three or four weeks (a minimum of two mowings) before using them as mulch. Consult the herbicide label for more specific instructions.
  1. Don’t use clippings from lawns that have a lot of weeds or that are diseased. Weeds that haven’t gone to seed are no problem mixed in with clippings. But if you’re cutting mature dandelion or other weed seed-heads, that seed could pop up later in the vegetable garden. Most lawn diseases won’t spread to vegetable plants, but it’s better to remove diseased plant parts and attached fungal spores than to transfer them elsewhere in the yard.
  1. Don’t pack fresh green clippings near live plants. Fresh clippings can break down quickly and generate heat in the process. That off-gassing and heat can harm plants, especially tender young ones like vegetable seedlings. Before using clippings as mulch, pile them out of the way for a week or two and use them after they’ve gone brown and dry.

Other clipping uses

Besides staying on the lawn or going into vegetable beds or paths, grass clippings can be used as mulch around flowers, shrubs, and trees. If you don’t like the brown straw-like look, top the clips with a light layer of wood mulch, bark, pine straw, or other common organic landscape mulch.

Or add the clippings to a compost pile, where their high nitrogen content is a perfect counterpoint to the high-carbon content of brown compost ingredients, such as leaves, shredded paper, straw, and/or sawdust.