Oregon State University
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Tanoak (Lithocarpus)

  • Fruit is an acorn with a spiny cap (not a scaly cap like most oak acorns).
  • Leaves are simple, alternate, and persistent.
  • Thick, persistent leaves have a silvery blue underside. Some leaves are toothed and some are smooth.
  • Buds are clustered on the ends of the twigs and piths are star-shaped.
  • Young leaves and twigs are densely wooly; many people are allergic to these hairs.



Tanoaks are an evolutionary link between the oaks and the chestnuts.  They look like oaks because their fruits are acorns, but their acorns have spiny caps reminiscent of the chestnuts.  About 100 species of tanoak occur in the world, but only one is native to North America, and it occurs in Oregon.  Because tanoak is not a true oak, its name is written as one word.

 For more information on the ashes native to the Pacific Northwest, go to the species page or see "Trees to Know in Oregon".

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