Mulch Refresh
When, how much, and what kind.
Mulch is not decoration. It is a slow-release fertilizer, a moisture battery, a weed suppressant, and a temperature buffer all at once. A well-mulched bed is doing four jobs you don't have to do.
Refresh once a year, in late winter or early spring before weed seed germination. Pull back any old mulch from plant stems, top-dress to a finished depth of 2 to 3 inches, and rake gently to break up any matted surface.
Depth: 2 to 3 inches is the sweet spot. Less than 2 and weeds break through; more than 3 starts to choke crowns and shed water.
Type: for ornamental beds, a medium-fine arborist chip or a dark hardwood fines is ideal. Avoid dyed mulches — the dye is fine, but the wood underneath is often pallet scrap that decomposes poorly.
For vegetable beds: straw or shredded leaves break down within a season and feed the soil. Bark is too slow and too acidic.
Never volcano. A cone of mulch piled against a tree trunk is the leading cause of premature tree death in residential landscapes. Mulch should sit two to three inches away from any woody stem.