Blue Oak is a California endemic of the hot, dry foothills surrounding the Central Valley, named for the striking blue-gray hue of its small, shallowly lobed leaves. It is one of the most drought-tolerant of all North American oaks, surviving on rocky soils with extremely low summer rainfall by going semi-dormant and closing its stomates during the driest months. Blue Oak woodlands are among California's most biodiverse terrestrial habitats, supporting over 2,000 plant and animal species.
Best time to see a Blue Oak
The best time to see a Blue Oak is May–September, when about 60% of U.S. sightings happen, based on 20,090 research-grade iNaturalist observations.
Not certain it is a Blue Oak? What plant is this? walks through what to check first and the lookalikes that catch people out.
Recent Blue Oak sightings near you
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