It is unconscionable that those involved in deciding to flood the plaza would sacrifice the health of this symbolic tree in order to limit public access to a public park and to suppress freedom of expression.
Saturated soil conditions are deadly to California Coast Live Oak trees (Quercus agrifolia). This is an evergreen species that requires good drainage. Unlike deciduous trees that can handle seasonal flooding by dropping leaves during the wet season, evergreen trees cannot. Flooding the surrounding soil eliminates oxygen which leads to the inability of roots to uptake water and nutrients. Such soil conditions also provide a hospitable environment for pathogenic fungi, which can infest roots and persist to bring about an earlier demise for the tree.
Though an exploratory investigation into the location of the oak roots has not been undertaken, anyone who believes that roots only exist within the circular planter is wrong. It should be noted, however, that the tree is planted at a lower elevation than the flooded area above, and therefore water is more likely to move inside of the cement wall and possibly inundate the roots within.
The value of the tree is likely more than $200,000 and possibly invaluable to the City as it cannot be replaced.
The over irrigation should cease immediately and the soil profile should be examined for signs of anaerobic conditions. The tree deserves a full investigation to determine where the roots are, what the level of soil compaction is, as well as what nutritional supplementation is required so that health mitigation treatments can be appropriately prescribed to ensure the tree can remain for another 200+ years.
This is the City’s most valuable tree and we do hope it is provided more respect than what is currently being shown.
Costello, Laurence R., Bruce W. Hagen, and Katherine Jones. Oaks in the Urban Landscape: Selection, Care, and Preservation. The Regents of the University of California Agriculture and Natural Resources, 2011.
Council of Tree and Landscape Appraisers. Guide for Plant Appraisal, 9th Edition. International Society of Arboriculture, 2000.