I have a chipper load of cedar and Douglas fir sawdust. Is that a good recipe to use as a mulch for rhododendrons and other shrubs and plants?
Lincoln County Oregon
Generally, coarser mulches are better than finer mulches. They allow water to penetrate to the soil. Finer mulches, like sawdust, can crust over and actually repel water. Mulches also have a high Carbon to Nitrogen ratio and when they are broken down by microbes, this process can compete for Nitrogen with plants with roots in the first 3-4 inches of soil.
If your chipper load is mostly wood chips (larger size) and not all sawdust (finer size), it should work okay as a mulch around the rhododendrons and other shrubs with larger and deeper root systems. For plants with shallower root systems, it may not be suitable.
Here is an Oregon State Extension publication (Mulching Woody Ornamentals with Organic Materials - EC 1629-E) that should be very helpful in selecting your mulching materials. https://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/ec1629.pdf