Why mulch breaks down
Organic mulch naturally decomposes over time, which is part of what makes it beneficial for soil health. As it breaks down, it also thins out and loses some of its weed-suppressing and moisture-retaining ability.
Signs it's time for a refresh
Faded color, a thin or patchy layer, and more visible weeds pushing through are common signs that a bed is due for fresh mulch.
Full replacement vs. topping off
Sometimes a thin top-off layer is enough. Other times, especially if the old mulch has compacted or developed a heavy layer, a full removal and replacement gives a cleaner result.