A new school of thought among arborists is gaining momentum: the vast majority of a tree’s problems don’t start in the canopy; they start in the soil.

This is because almost all urban soils are deeply degraded. Eroded by development and depleted by chemical fertilizers, herbicides, and pesticides, the vital soil food web—which begins with microbes—is often completely broken.

Just as humans need gut bacteria to digest food, plants rely on soil microbes to process theirs. Plants naturally transfer sugars into the ground, trading them for vital nutrients and minerals found underground. This beneficial network of microbes and fungi also retains water, defends the plants against disease, and breaks up heavy soil compaction.

Despite a beautiful variety of plantings on the Temple grounds, several trees—including camellias, Japanese maples, a variegated cedar, Callery pears, and the stately Bodhi tree—showed clear signs of stress. Laboratory analysis of the soil nutrients revealed an overabundance of some nutrients but low nitrogen (synthetic nitrogen washes out of the soil quickly). These imbalanced nutrient levels, combined with the visibly stressed trees, strongly indicate a stalled biological system: the plants have plenty to eat but no way to process it.

To address the root cause (pun intended), we recently injected Oath Soil Life, a biological inoculant containing a robust consortium of beneficial microbes and mycorrhizal fungi, to help rebuild a healthy soil food web. 

It typically takes five to six weeks to see some above-ground improvements, and potentially a year to restore the biome’s basic foundations. We will follow up with one to two more treatments this year to ensure these new microbial communities establish themselves.

It is a hands-on reminder of nature’s profound interconnectedness: the magnificent life we see above ground depends entirely on the harmonious, unseen network working tirelessly below.

If you’re curious to learn more about soil microbes, reach out to [email protected].