@jhigbie Is this your Mystery Oak? On Sunset Trail. Yesterday I was there, and wondering what you were talking about (after hiking here decades), and there it is!!! Only micro acorns seen, couldn’t find any galls. Nestled among Leather Oaks with a couple small Coast Lives nearby. I’ve read that apparently one of the parents doesn’t need to be nearby. So maybe Q. durata durata with Valley Oak, which are close enough as the pollen flies. Fascinating! @sandy_b

Apologies for the lower-quality photos. Growth habit is too large and expansive to be pure Q. john-tuckeri, but the leaf size (smaller but wide) and shape matches for a hybrid. Some of the leaves have the tooths of Q. john-tuckeri but others are a bit rounded and have slight lobing like Q. douglasii.

Nearby oaks include Q. berberidifolia, Q. lobata, Q. john-tuckeri, and Q. douglasii.

Was originally thinking this was a straightforward Q. douglasii, now examining the leaves closer, it appears some Q. lobata introgression is likely based on larger size and leaf lobing.

Also possible there's just a wide range in Q. douglasii (and other white oak) phenotypes, and this is just on one end of the spectrum.

Within 15' of following Quercus observation.

note at upload (2018): looks intermediate between a coast live oak and a blue oak, but probably a canyon live oak crossed with blue oak

Updated note (3/2023): No documented hybrids between oak sections, seems more likely Q. douglasii with either Q. berberidifolia or Q. john-tuckeri

Reference for Q. x alvordiana:
https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=40533

Engelmann Oak; San Gabriel Valley;This is one of few such trees in the immidiate area that appear to be the remnant of a woodland that was once more widespread. The species has become threatened and highly encroached upon by urban development.