Select the proper mulch for your hillside. If you want to use an organic mulch, use long, fibrous shredded bark pieces. They will not blow away or float away as easily as larger bark pieces. If you use inorganic mulch, use gravel or shredded tire rubber.
Lay the mulch down on the hillside at a depth of 3 to 4 inches. Do not let the mulch touch the base of your plants. Rake the mulch into an even layer with a garden rake.
Refresh the mulch layer once to twice a year to replace any mulch lost to rainfall. If you are use organic mulch, you will also lose mulch to decomposition.