Taken at a distance from the kitchen window

Charlie has developed a new activity. He takes himself out to the garden and lays down on the soil for a few minutes. He then comes inside covered with all the mulch/soil that has stuck to his fur. He drops all the bits and pieces through the house, on the lounge and carpet. My ever ready stick vacuum cleaner is brought out to clean the floors. The lounge is cleaned with all things sticky. Fortunately the lounge has covers. He is doing this on a number of occasions per day.

When visitors arrive I take the covers off the armchairs as they will have garden soil pieces on them.
 
I have tried to putting pavers where he lays but he just found another spot. I have decided to just accept it. I do wonder if it is boredom (his dog sibling died recently) or a health issue. To be monitored.