The answer to 'hedge erosion' is that it is a common problem for homeowners with hedges or shrubs on sloped or hilly terrain. Hedge erosion occurs when soil and mulch around the base of the plants gets washed away, exposing the roots and causing the hedge to become unstable or even collapse.
Common causes of hedge erosion include heavy rainfall, runoff from gutters or downspouts, and poor soil drainage. Symptoms include the hedge leaning to one side, exposed roots, and soil loss around the base. Solutions can include improving drainage, adding retaining walls or terracing, and replanting the hedge in a more stable location.