Many urban trees are growing in poor conditions, such as highly compacted soils low in organic matter and microbial life. In an urban environment, leaf litter that decomposes and provides natural fertilizers for our trees is cleared away. Grass is planted under trees, creating competition for water and nutrients, and then mowed with heavy equipment that compacts the soil. When homes are built, topsoil is removed and roots are damaged. Traditional fertilizers high in Nitrogen, can produce excessive canopy growth, which can be problematic when trees lack the required root system to support extra growth. These things combined can leave trees in a weakened state, predisposing them to attacks from insects and disease.