Quercus chrysolepis | Santa Cruz Mountains
The Santa Cruz mountains are home to a substantial number of large to huge Canyon Oaks (Quercus chrysolepis). These trees are growing in-habitat with Coast Redwood (Sequoia sempervirens), and thus receive copious rainfall in typical years. These are mountain refugia, with redwoods growing at two thousand feet receiving 60 inches or more of rainfall per year, while the Santa Clara Valley below typically receives fifteen inches. This is why Redwoods planted in the Valley below are typically in such terrible condition - even though they are "native" a few tens of miles away, Redwood is not in any meaningful way native to the Santa Clara Valley. But on the mountain, the droughts of recent centuries have been insufficient to kill the vaunted Redwoods, which means they have also been insufficient to kill the more drought tolerant Canyon Live Oaks, thus allowing these trees to survive for hundreds, if not thousands, of years. We will not be delving into Canyon Live Oak for our current purposes, because the trees simply do not tolerate the soils of the valley below their native range. Descending the Santa Cruz Mountains, Canyon Live Oaks disappear by fifteen hundred feet or so. Attempts to grow this species at Stanford has failed, and of the Canyon Live Oaks planted in the Shields Grove, one of the pair died early on, and the survivor looks terrible, despite the soils which Davis is known for. The same phenomenon is true of the other famous tree species that grows in habitat with Canyon Live Oak and Coast Redwood, the lovely Pacific Madrone (Arbutus menziesii), which are exceedingly rare in the valleys below the Santa Cruz Mountains, despite what are certain to have been myriad attempts to grow it there.