Ring-cupped oak is an evergreen oak from East Asia, and its name comes from the acorn cup, which is wrapped in instead of the overlapping scales of American oaks. It isn't native to the United States, but it's sometimes planted as an ornamental tree where winters are mild. It's also called Japanese blue oak.
Appearance
- Growth form
- An evergreen tree usually up to about 65 ft (20 m). Bark is smooth and gray when young and becomes rougher with age.
- Leaves
- Leathery leaves are 2.5–5 in (6–13 cm) long, with shallow teeth only on the upper part. They're glossy green on top and bluish gray underneath, with flat silky hairs. New growth comes out purple, chocolate, or burgundy.
- Fruit
- Acorns are about 0.6–0.8 in (1.5–2 cm) long, pale or reddish brown, and ripen in their first fall. The cup covers a third to half of the nut and has 5–7 rings.
Look-alikes
Chinese evergreen oakQuercus myrsinifolia
Turn a leaf over: ring-cupped oak has flat, silky hairs on the bluish-gray underside, while Chinese evergreen oak's leaves lack them and are usually slimmer. You may need a hand lens to see the hairs.
Why they get mixed upBoth are Asian evergreen oaks with ringed acorn cups, and nurseries often mix them up.
Where it lives
- Typical habitats
- Evergreen broadleaf forest
- Hillsides
- Gardens and parks
- Range
- Native from the western Himalayas (Afghanistan, India, Nepal, Bhutan) across much of China to Taiwan, Vietnam, southern Korea, and western Japan, at about 330–8,500 ft (100–2,600 m). In the US it's grown only as a planted ornamental.
- Preferred conditions
- In cultivation it's rated to about USDA zone 7. Young trees can be hurt by late spring frosts, and trees cut back by hard cold have resprouted.
Growing it
- Care
- Tolerates pruning well and is used as a hedge in Japan. It doesn't like being transplanted.
Conservation
- IUCN Red List
- LCLeast ConcernLow risk of extinction
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