Moss is beautiful but it does not belong growing in sidewalks joints and pavement cracks. Apart from the appearance, moss growing in cracks provides a foothold whereby other plants potentially widen the crack.
There is a mild hazard risk due to tripping or slipping. Moss is slippery and while its lovely on rocks and logs in your shady flower garden it does not belong on driveway pavement or sidewalks. A sidewalk-friendly moss removal solution is required.
Pressure Washing Car Wash Nozzle to Remove Moss
Using a high-pressure washer such as for washing your car or the vinyl siding of your house works very well. The high pressure avoids the use of herbicides for the environmentally conscious and the high-pressure will also flush away dirt, roots and light surface stains.
The moss that is evacuated is fine for composting as it was not subjected to chemical or plant killer. You want to employ sidewalk & concrete-friendly removal methods wherever feasible. Moss grows in shady, moist areas. If your sidewalk is mostly shaded, consider mild to moderate pruning of trees and tall shrubs near the pavement. More exposure to the sun will help prevent moss from growing where it does not belong.
Another more aggressive tactic is to sprinkle powdered laundry detergent along the cracks, covering the visible moss. The alkalinity of the detergent will kill the moss and the following day this can be rinsed away. This however will leave the sidewalk slippery for a time, so consideration of pedestrian foot traffic should be taken.
More aggressive moss-removal would be to use commercial moss-specific herbicides, or to use potassium salts. Potassium Nitrate can be easily produced at any garden center from retailers like WalMart, Home Depot, True Value, etc.) is the form of "Tree Stump Remover."
Potassium Nitrate (Tree Stump Remover) for Removing Pavement Moss: A Safe Weed Killer
The Potassium Nitrate is sprinkled over the moss and allowed to sit overnight. That should be adequate to kill and partially dissolve and dislodge the moss which can not be easily rinsed away. In this case, discard the organic debris in the trash and not into your compost pile.
Potassium Nitrate (KNO3) is a white crystalline chemical that is found in nature as 'saltpeter' and is commercially prepared from interaction of Potassium Chloride and Sodium Nitrate.
Decomposing Potassium Nitrate (dissolving in water water) causes it to release much Oxygen, an action that helps kill organic material much the same way Hydrogen Peroxide does. Although Potassium Nitrate has been used in gunpowder for centuries, it is safe for use as prescribed here. In fact, Potassium Nitrate is often used as a food preserver (usually for meats.)
Potassium Nitrate inhibits the growth of bacteria on meat and in the case of moss growing in pavement cracks, prevents growth of plant life there too.