Mexican Blue Oak (Quercus oblongifolia) is native to the United States, growing from Arizona, New Mexico, and Texas, south through the Sierra Madre mountains of northwestern Mexico, and continuing south to central Mexico. Mexican blue oaks also occur in central Baja California. Geographically, this is quite a large range, suggesting a similarly wide range of environmental adaptation.

Just north of the Mexican blue oaks in Baja grows the closely related Engelmann oak (Quercus engelmannii), which ranges from northern Baja, northward to the Los Angeles area in California. Though closely related to the Engelmann oak, Mexican blue oak has foliage that is slightly, too much, bluer in color, with generally smaller leaves, giving the tree a finer-textured appearance than its California cousin. Mexican blue oak is also a more uniform species than the variable Engelmann oak, with a consistent urban-friendly upright growth habit, and a striking blue coloration.

Summer monsoon rainfall is typical within the native range of Mexican blue oak, giving the tree natural tolerance to conservation appropriate summer irrigation, and a landscape friendliness better than almost all California native oaks. Relatedly, resistance to powdery mildew is common to oaks throughout the part of the world where Mexican blue oak grows due to summer monsoons. In California, coastal maritime summer humidity driving powdery mildew infection limits the oceanward range of many oaks, but thus far Mexican blue oak has shown good resistance, proving more resistant to powdery mildew than many Engelmann oaks.

The fine bluish texture of the Mexican blue oak makes it a real favorite among those in the California landscape industry who have seen the tree in person. At least one California nurseryman has been heard to joke that the best Engelmann oak to grow is, in fact, the Mexican blue oak. Mexican blue oak is highly recommended for trial on good draining, uncompacted sites throughout coastal and interior California. Limited testing of Mexican blue oak in areas of major maritime influence is recommended. The first five years of growth of Mexican blue oak at Apple Park in Cupertino has been very positive.