Engelmann Oak, mesa Oak, Pasadena Oak
The mesa oak is an evergreen oak that is native to our local area from Hemet to Pasadena.
James Heinrich of the Los Angeles County Arboretum & Botanic Garden wrote a an excellent article for Pacific Horticulture (April 2012 issue). The following are his recommended cultural requirements of this majestic tree species.
Some assume that, because this oak is native to southern California, it will tolerate all of the climatic vagaries handed out by Mother Nature, and be plastic enough to adjust. Most authorities recommend that, when the annual precipitation is below normal (fifteen inched), supplemental deep and thorough monthly watering through spring is advisable. If summer temperatures are above normal (with extended periods of heat), one or two supplemental applications of water are also advisable (in August and/or September). Apply the water several feet from the trunk, well into the drip zone and beyond. Keeping the water away from the trunks helps avoid concentrated amounts of water soaking directly onto the main roots, which are the most susceptible to Armillaria (a deadly disease of oaks). Any pruning should be restricted to the month of September, when the trees are most dormant.