Quercus engelmanii x | Santa Rosa Plateau
We have already discussed the wide-ranging genetics of Engelman Oak visible in field inspection. To further complicate matters, Engelman Oak often grows adjacent to areas of chaparral, which in turn host related scrub oaks, which in turn share pollen with true Engelman Oaks, creating hybrids. An example of such a hybrid can be seen in this photo from the Santa Rosa Plateau. The hybrids come across as half-size, or quarter-size, Engelman Oaks, perhaps with slightly greater density. These will occur on the margins of the deeper soils which grow tree form Engelman Oaks, and the thinner, generally upland chaparral soils, supporting the shrub oaks.