leaves, straw, peat moss, etc., spread on the ground around plants to prevent evaporation of water from soil, freezing of roots, etc.
transitive verb
to apply mulch to
See mulch in American Heritage Dictionary 4
(mŭlch)
noun
A protective covering, usually of organic matter such as leaves, straw, or peat, placed around plants to prevent the evaporation of moisture, the freezing of roots, and the growth of weeds.