We don't have synonyms for mulches yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are gulches, mulched and munches.
(n) :
(agriculture, horticulture) Any material used to cover the top layer of soil to protect, insulate, or decorate it, or to discourage weeds or retain moisture.
(n) :
(agriculture, horticulture) Any material used to cover the top layer of soil to protect, insulate, or decorate it, or to discourage weeds or retain moisture.