Historically, we have seen that squirrels, birds or other small animals like to use mulch as a hiding place for nuts, berries and other things they transfer from the surrounding outdoors. Also, in the spring, Maple trees drop “helicopter seeds”. These can root in mulch. We suggest lightly raking through your problem spot to see if you can find what the cause of the problem is. If nothing is noticeable, you can apply Preen to the area.