Common Name: ring-cupped oak
Type: Broadleaf evergreen
Family: Fagaceae
Native Range: China, Japan
Zone: 7 to 9
Height: 20.00 to 30.00 feet
Spread: 10.00 to 15.00 feet
Bloom Time: April to May
Bloom Description: Yellowish-green
Sun: Full sun
Water: Medium
Maintenance: Low
Suggested Use: Shade Tree, Street Tree
Flower: Insignificant
Leaf: Evergreen
Other: Winter Interest
Culture
Best grown in rich, humusy, medium moisture, well-drained soils in full sun. Adapts to a wide range of soils including dry ones. Tolerates clay soils. Not winter hardy to the St. Louis area.
Noteworthy Characteristics
Quercus glauca, commonly called ring-cupped oak, is an evergreen oak that is native to Japan, China, Korea, Taiwan and the Himalayas. It is an upright-oval to rounded tree that typically grows in cultivation to 20-30' tall. In its native habitat, it may mature over time to as much as 30-50' tall, but is also often seen growing as a large shrub. Leathery, oblong to elliptic leaves (to 5 1/2" long) are a glossy dark green above and glaucous gray-green below. Leaves are toothed near the apex. New leaves emerge with bronze tints. Foliage may turn yellow-green in winter. Insignificant, monoecious, yellowish-green flowers in separate male and female catkins appear in spring. Fruits are acorns (to 3/4" long) with cups that extend to approximately 1/3 of the acorn length. Each cup has 5-6 concentric rings. Acorns appear singly or in clusters of 2 or 3. Bark matures to a rough black-brown with fissures.
Genus name comes from the classical Latin name for oak trees.
Specific epithet means with a bloom or whitish, powdery coating.
Problems
Ring-cupped oak is considered to be a low-maintenance tree with good pest resistance, but is only winter hardy in USDA Zones 7-9. Oaks in general are susceptible to a large number of diseases, including oak wilt, chestnut blight, shoestring root rot, anthracnose, oak leaf blister, cankers, leaf spots and powdery mildew. Potential insect pests include scale, oak skeletonizer, leaf miner, galls, oak lace bugs, borers, caterpillars and nut weevils.
Uses
Where winter hardy, this evergreen oak serves as a small shade tree in the landscape. It may also be grown as a tall screen or shrub.