In my, admittedly limited experience, people seem to use the common name Oregon White Oak for this species when it is predominately large trees in oak savanna habitat in the lower elevations on the west side of the Cascades, and Garry Oak for the dense stands of smaller and more slender trees which grow in more arid areas with less topsoil in the eastern part of its range. But they are both the same species of tree. There is even a subspecies, Q. breweri, which is a colony forming shrub seldom growing more than 10’ tall, and is endemic to the Siskiyous.
They are the only native oak in our region north of Lane County, Oregon. They are also the only deep and round lobed oak one may encounter north of Lane County. Most escaped cultivars have pointed lobes on the leaves, and one has shallow rounded lobes.
It is the primary larval host for, among many others, the butterfly Erynnis propertius (Propertius Duskywing) and the moths Nadata oregonensis, Acronicta marmorata (Marble Dagger Moth), Perigonica tertia, and Cissusa indiscreta (Indiscete Cissusa Moth), as well as a common larval host for dozens of other Lepidoptera
Quercus garryana grows throughout the western part of our region, extending east in a few riparian valleys. Due to habitat loss from development and encroachment from faster growing conifers, the population is on the decline. But preservation and restoration efforts are underway in many of it’s historical locations.
Size- Up to 100’ tall
Habitat- Rocky, well drained soil
Range- West side of Cascades; some eastside riparian valleys