Q: I have a dog run area adjacent to my back patio. It is covered with cypress mulch. The mulch is absorbing urine and this time of year the mulch is not drying out. Do you have any suggestions for something to spread in the area to “deodorize” the ground? There are plantings downhill that might be impacted with runoff when it rains.
A: Urine has a noxious smell when it is converted to ammonia-type compounds rather than odorless nitrogen gas. In cold weather, bacteria, soil organisms and plants that normally change urea to smell-less compounds are inactive. If the urine isn’t washed out of the mulch by rain, it “sours” and smells bad.
The best plan I can offer is to plant a tough, evergreen groundcover (like liriope or mondo grass) below the dog run and wash the urine there in winter.