Why Miami sidewalks go green first
The city sidewalk sits in the swale under the street trees, and in Miami that means live oak, ficus, black olive or mahogany. It gets the leaf drop, the shade and the sprinkler overspray from the swale grass, and it stays damp when the sun-facing driveway has dried. Algae wants exactly that. So the sidewalk goes green months before the driveway does, and once it is green it holds water and gets slick. A pre-treatment kills it; the surface cleaner lifts what is left.


