Answer: Fresh grass clippings contain a good measure of nitrogen, but there are a few cautions to consider before using them as a mulch. Fresh clippings tend to mat down as they decompose, which may prevent water from reaching the soil if it's being applied over the top. It isn't likely that any seedheads contained in the clippings will sprout into new grass plants because the heat generated in decomposition will kill off the seeds. However, I'd recommend spreading them out and allowing them to dry before using them as a thick weed suppressing mulch material.
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