Engelmann Oak, an endangered subtropical wonder

The bluish-green, glaucous, and ovate leaves of the spectacular Engelmann oak (Quercus engelmannii) resemble Eucalyptus gamophylla or cinerea more than other oak species. Also called the Mesa oak, this endangered tree reaches 60 feet tall and a massive 90 feet wide when mature. Its gnarled black branches once twisted wildly over grassy plateaus in Baja Mexico and California, where it is native, although its striking silhouette makes it look like it belongs in the Serengeti, sprawling over a tropical African savanna. These days it is a rare sight, having been nearly eliminated from the mesas and grasslands because these flat sites are ideal for development. They also require a significant amount of rainfall: at least 15 inches annually. This need limits their natural range to a narrow band along the coast. They can become drought-deciduous, but they favor areas where there is a source of summer water, whether from springs, streams, aquifers or monsoonal rains. Of the remaining wild stands, 93% are located in the Cleveland National Forest in San Diego County, and 6% are on the Santa Rosa Plateau (although this stand was decimated by a wildfire several years ago). Our property in De Luz, a micro plateau nestled directly between these two areas, owes its location to the fact that we have about 20 specimens at various stages of maturity. In an effort to preserve this magnificent species, we will be planning our home and gardens on the mesa around these giants. I am eager to see if, in the coming months, they become deciduous. If they do not, it would indicate that their root systems have access to an underground water source.