Pine Bark Mulch is the bark from a pine tree. It is a great way to lower the ph of soil and to add organic matter.
As it decomposes into the soil it adds acidity. It is therefore necessary to add a tbhick layer of pine bark mulch every 3-4 months, but please make sure when using it to not have it touching the branches of the plant. This may cause the branches to rot and get infected especially with new (one and two year old branches).
Remember to keep the mulch away from the trunk or branches, though.