mulch

Any material used to cover the top layer of soil to protect, insulate, or decorate it, or to discourage weeds or retain moisture.

“An organic mulch is a mulch made of natural substances such as leaves or grass clippings.”

A material used as mulch, as a decorative redwood bark mulch.

To apply mulch.

“Mulch your vegetable garden to retain moisture and keep weeds down.”

To turn into mulch.

“I decided to mulch the grass clippings.”