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by D. Muffly
GENERAL INFO
Quercus oblongifolia is a hardy evergreen oak that is adapted to drought, heat, fire, and alkaline soils. This well-shaped tree is valued primarily for its contorted, spreading branches and strikingly blue, waxy foliage. While sometimes confused for Q. engelmannii, this species has a more upright habit and slightly smaller leaves. It is browsed by deer and bighorn sheep, while its acorns are enjoyed by squirrels and birds. It is resistant to sudden oak death and aphids. Additionally, resistance to powdery mildew allows it to thrive in humid coastal environments.
Native range: southwest United States, MexicoEthnobotanical Info / Tree Use: The acorns of Mexican Blue Oak are a staple food of Native American Tribes in the Southwestern US. These acorns can be ground or leached to remove their bitter tannins. Another traditional method involves burying them in the ground to overwinter, which is also effective in removing their astringent flavor. Citations Page
Native range: southwest United States, MexicoEthnobotanical Info / Tree Use: The acorns of Mexican Blue Oak are a staple food of Native American Tribes in the Southwestern US. These acorns can be ground or leached to remove their bitter tannins. Another traditional method involves burying them in the ground to overwinter, which is also effective in removing their astringent flavor. Citations Page
TREE CHARACTERISTICS
Tree Shape: RoundedFoliage Type: EvergreenMaximum Tree Height: 60 feetCanopy Width: 20-30 feetGrowth Rate: ~36 in/yearLeaf Arrangement and Leaf Form: Alternate, SimpleLeaf Shape: OblongLeaf color: Blue GreenFlowers: InconspicuousFlower Color: Brown or YellowFlower Time: SpringFruit: Small Brown AcornFruiting time: FallFruit Value: Wildlife use itBark Color: Light Gray, Furrowed, Ridged, ScalyLitter Type: Dry Fruit, Leaves
SITE CONDITIONS
Recommended Planting Area: Greater than 7'Water Use Rating: LowSunset Climate Zone: 7 - 9, 14 - 24Shade Tolerance: NoUSDA Hardiness Zone: 7, 8, 9, 10Soil Texture: Loam or SandSoil pH: Neutral to AlkalineSalt Tolerance: Moderate
CONSIDERATIONS
Branch Strength: StrongRoot Damage Potential: ModeratePotential health issues: Allergy, PoisonousWildlife interactions: Attracts birds, squirrelsDisease and Pest susceptibility: Armillaria, Root Rot and Invasive Shot Hole Borer, Coddling Moths, Mistletoe, SpittlebugsDisease Resistance and Pest Resistance: Powdery Mildew, Sooty Mold, Sudden Oak Death, Verticillium and AphidsAphidsUtility Friendly: No
External Resources
CITE THIS TREE
"SelecTree. UFEI. "Quercus oblongifolia Tree Record." 1995-2025. Cal
Poly State University, San Luis Obispo. Accessed on Jun 5, 2025."
< https://selectree.calpoly.edu/tree-detail/1259 >
< https://selectree.calpoly.edu/tree-detail/1259 >
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