Tree Blog

Quercus agrifolia | SoCal New Growth

Coast Live Oak (Quercus agrifolia) varies in subtle ways throughout its range, as is common with oaks. At the extreme is Quercus agrifolia var. oxyadenia, a southern California variety known for extremely long acorns. But more subtle variations also occur, and differences in the color of the new growth is another widespread variation seeing more yellowing new growth in northern California, and more red new growth in southern California. Interestingly, observations in the Santa Cruz mountains of northern California show a mixture of new growth colors. The reddish coloration is indicative of California Black Oak (Quercus kelloggii), and anecdotal observation suggests that there has been long term introgression of Black Oak into the Coast Live Oak gene pool, driven by the extent of overlap of the two species in a particular ecozone. In northern California such overlap largely occurs in the mountainous zones, while in southern California it appears to occur throughout its narrow range.

Dave Muffly