Quercus glauca (syn. Cyclobalanopsis glauca, Q. annulata), also known as Ring-cupped Oak, Japanese Blue Oak or Glaucous-leaf Oak, is a species in the genus Quercus, native to Asia from Afghanistan east to southern Japan (アラカシ;粗樫), Taiwan (青剛櫟), and Vietnam.
It is a small to medium-sized evergreen broadleaf tree growing to 15-20 m tall. The leaves are a distinct deep purple-crimson on new growth, soon turning glossy green above, glaucous blue-green below, 6-13 cm long and 2-5 cm broad, with a serrated margin. The flowers are catkins, and the fruit are acorns 1-1.6 cm long, with an intricate ring pattern on the acorn cup.
Read more about Quercus Glauca: Cultivation and Uses