A major component of growing a healthy tree is the presence of microorganisms in the soil. Building soil saves water because healthy loam soil has the capacity to hold water longer, and moist soil supports the growth of microorganisms. As soil biologist Dr. Elaine Ingham (2000) explains, “Many organisms enhance soil aggregation and porosity, thus increasing infiltration and reducing runoff”. Through the process of improving the soil structure, the soil food web becomes more developed, and with it encompasses the multitude of bacteria, amoebas, flagellates, ciliates, nematodes and fungi that help grow plants.  Different plants prefer the presence of a different balance of microbes, and this influences the role of succession of plant communities in a natural system.

Mutualist fungi are of particular importance for tree growth.  Fungal hyphae extend past where roots can reach, and through the mycorrhizal association, aid in the tree’s access to water and nutrients.  As such, “The presence of mycorrhizae (fungal modified tree roots) can act to moderate early drought stress in trees” (Coder 2012).

The City offers low cost mulch at the Buckman Road Recycling and Transfer Station (BuRRT) as well as compost from the City Waste Water Treatment Plant (SFSWMA 2019). By adding these components to the landscape at small and large scale, microbes are able to decompose decaying plant matter, make nutrients more bio-available for plant roots, consume pollutants, and regain balance with pests and pathogens. Through no-till practices, existing hyphae remains intact and supports a wider community of plants with compounding ecosystem benefits.


Fungal hyphae physically bind soil particles together, creating stable aggregates that help increase water infiltration and soil water holding capacity.”

Dr. Elaine Ingham (2000), soil biologist