How Much Bark?
Refreshing the bark/mulch in your landscape can really help to clean up the look of your landscape. One question that we often get is how much bark should I add to my landscape? It is often not as much as you think.
Once you have an established landscape bed completely finished, all of the bark that is there is still doing the job that it is suppose to. It helps to keep moisture near the plants, it helps to shade out weeds, and it is slowly creating organic matter that is beneficial for the plants. This depth typically is between two and four inches of bark in its various stages of life and decomposition.
When it comes time to replenish the bark, just a skim coat is needed. All of the old bark below the new is still functioning like it should. All that is needed is to refresh the color of the top, and add a little bit of new material for continued decomposition.
Adding a new thick layer on top will not do much for your landscape. It will cause a backlog of needed decomposition. But it will not help to stop the weeds any more than just a thin new layer will. Weed seeds will blow in with the wind and sit on top and start to establish themselves.
Once your landscape is established, all that you need to do is to just add a thin new fresh layer of bark to clean up the look. And in this case, more is not actually more. It is just wasteful.