Conifer needles that drop at the end of a season form an ideal natural mulch in the forest.
They help prevent erosion, allow water to percolate more easily into the soil and control weeds. Likewise, we can benefit our gardens by applying a fresh layer each year. Most of the literature refers to pine needles, probably since pine is present over much of the U.S. and populated Canada. A thin layer of fir needles will work in the same way. These needles are acidic and tend to promote a slightly more acidic surface layer. They are, therefore, an ideal mulch for acid-lovers such as azalea, rhodendron and pieris.