Quercus x jolonensis | Stanford Dish
Surveying oaks on the Dish at Stanford, one finds some big, old trees which defy clear categorization into Blue Oak or Valley Oak. These are the hybrids known as Jolon Oaks, which occur whenever Blue Oak and Valley Oak grow together. Oaks are typically, in their genetic inheritance, maternally biased. A hybrid will usually turn out to be more like Mom than Dad. This concept proves quite useful when attempting to identify patterns of hybridization. The bluish foliage color is a potentially confirming trait.