Answer: Mulch can solve a number of problems. It can cover soil and form an attractive cover. It can retain moisture in the soil. It can feed the soil. It can help keep weeds under control. If you are growing perennials you can either cover up the old organic mulch or refresh it. If it hasn't fully decomposed, I'd rake away the old before adding the new. If it's mostly decomposed, then just add some new mulch on top.
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