University of California
Western Tree Failure Database/California Tree Failure Report Program
Facebook
X (Twitter)
Reddit
Pinterest
Tumblr
LinkedInQuercus agrifolia summary comparisons
Coast live oak is the most commonly reported species in the CTFRP database. (See CTFRP Statistics/50 or more) It is the most widely planted native California oak in urban landscapes. Many remnant coast live oaks of great age can be found within developed areas. It is an evergreen oak native to the Coast, Transverse and Peninsula ranges.
The data for 1995 in the comparison table is derived from Edberg, R J. and Berry, A. M. 1999. Patterns of Structural Failures in Urban Trees: Coast Live Oak (Quercus agrifolia) Journal of Arboriculture 25(1). The data (in more detail) for 2014 was published in Western Arborist Magazine, Summer 2014. (See Quercus agrifolia 2014).
Quercus agrifolia (coast live oak) summary comparison 1995/1996, 2010 and 2014
| 1995 | 1996 | 2010 | 2014 | ||
| All species | 1467 | 2023 | 4886 | 5589 | |
| Q. agrifolia | 122 | 161 | 526 | 619 | |
| % of total | 9% | 8% | 11% | 11% | |
| Location of failure | trunk | 29% | 33% | 37% | 37% |
| branch | 26% | 28% | 24% | 23% | |
| root | 45% | 39% | 39% | 40% | |
| Mean DBH | 35 in. | 34 in. | 33 in. | 32 in. | |
| Mean height | 48 ft. | 49 ft. | 48 ft. | ||
| Mean age | 101 years | 89 years | 89 years | ||
| Site categories | park | 17% | 14% | 14% | |
| residential | 57% | 55% | 51% | 50% | |
| street | 5% | 7% | 8% | ||
| Site use % of total | high | 38% | 37% | 41% | |
| medium | 29% | 23% | 24% | ||
| low | 20% | 25% | 23% | ||
| Stand type % of total | natural | 80% | 72% | 65% | 66% |
| planted | 16% | 13% | 13% | ||
| mixed | 12% | 22% | 21% | ||
| Tree occurrence | alone | 43% | 35% | 36% | |
| in a group | 39% | 49% | 49% | ||
| altered stand | 18% | 15% | 15% | ||
| Trunk defects | multiple trunk | 28% | 32% | 35% | |
| failed portion dead | 19% | 15% | 14% | ||
| lean | 13% | 9% | 9% | ||
| decay present | 97% | 87% | 79% | 80% | |
| Trunk point of failure | above ground level | 46% | 63% | 58% | 57% |
| Branch defects | heavy lateral limbs | 31% | 34% | 33% | |
| included bark | 12% | 7% | 12% | ||
| decay present | 73% | 69% | 70% | 74% | |
| Branch point of failure | at attachment | 40% | 47% | 49% | |
| Root defects | decay present | 78% | 73% | 71% | 73% |
| lean | 15% | 17% | 27% | ||
| one-sided | 13% | 15% | 15% | ||
| failed portion dead | 11% | 22% | 15% | 16% | |
| none | 12% | 10% | 10% | ||
| Precipitation % of total | some | 53% | 74% | 47% | |
| none | 47% | 26% | 53% | ||
| Wind % of total | <5mph | 49% | 43% | 53% | 39% |
| 5-25 mph | 31% | 26% | 31% | ||
| >25 mph | 26% | 21% | 29% |