Soil builds up real fast. A few leaves here and there, some dust, a little water and boom: grass, bushes, flowers. All this in several weeks to months. I've see

Soil builds up real fast. A few leaves here and there, some dust, a little water and boom: grass, bushes, flowers. All this in several weeks to months. I've seen it happen so many times because our streets aren't well maintained. 5cm soil on concrete, asphalt, rooftops, etc.