(August) We recently moved into a new house and we have a brand new yard. We are
experiencing something else new for us -- a weird fungus that appears only in
the bark. It looks like someone spilled dry mustard. What is this and what
should we do about it?
Organic mulch will break down over time into humus. Microorganisms, and bacteria help in this process. Occasionally, you will see white stringy matter or yellow growth, sometimes even some small mushroom like material. It is normally nothing to worry about, but simply nature doing its job. If what you see is disturbing, then raking or hosing it down can move it into the interior of the pile, and you won't have to watch. It should not be harmful to your plants.