ENH-705

Quercus glauca: Blue Japanese Oak1

Edward F. Gilman and Dennis G. Watson2

1. This document is ENH-705, one of a series of the Environmental Horticulture, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date November 1993. Revised December 2006. Reviewed May 2011. Visit the EDIS website at http://edis.ifas.ufl.edu.

2. Edward F. Gilman, professor, Environmental Horticulture Department; Dennis G. Watson, former associate professor, Agricultural Engineering Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county’s UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.

IntroductionAt first glance, this plant would hardly be thought to be an oak. Creating a very formal, dense, round or oval shade, evergreen blue Japanese oak grows slowly to 25 to 40 feet in height with a spread of 25 to 35 feet. The new growth is often bronze- or purple-tinted, and develops into shiny, dark green, 2.5- to 5.5-inch-long by 1- to 2.5-inch-wide, leathery leaves. It is a very attractive tree suited for many uses.

General InformationScientific name: Quercus glauca

Pronunciation: KWERK-us GLAW-kuhCommon name(s): Blue Japanese oak, ring-cupped oakFamily: FagaceaeUSDA hardiness zones: 8A through 9B (Fig. 2)Origin: not native to North AmericaInvasive potential: little invasive potentialUses: street without sidewalk; parking lot island 100-200 sq ft; shade; parking lot island > 200 sq ft; tree lawn 3-4 feet wide; tree lawn 4-6 feet wide; tree lawn > 6 ft wide; highway medianAvailability: not native to North America

DescriptionHeight: 25 to 40 feetSpread: 25 to 35 feetCrown uniformity: symmetrical

Figure 1. Middle-aged Quercus glauca: blue Japanese oakCredits: Ed Gilman, UF/IFAS

Figure 2. Range

2Quercus glauca: Blue Japanese Oak

Crown shape: round, ovalCrown density: denseGrowth rate: slowTexture: medium

FoliageLeaf arrangement: alternate (Fig. 3)Leaf type: simpleLeaf margin: serrate, dentateLeaf shape: oblong, obovate, elliptic (oval)Leaf venation: pinnateLeaf type and persistence: broadleaf evergreen, evergreenLeaf blade length: 2 to 4 inches, 4 to 8 inchesLeaf color: greenFall color: no color changeFall characteristic: not showy

FlowerFlower color: brownFlower characteristics: not showy

FruitFruit shape: oval, roundFruit length: .5 to 1 inchFruit covering: dry or hardFruit color: brownFruit characteristics: does not attract wildlife; not showy; fruit/leaves a litter problem

Trunk and BranchesTrunk/bark/branches: branches droop; not showy; typi-cally one trunk; thornsPruning requirement: needed for strong structureBreakage: susceptible to breakageCurrent year twig color: green, brownCurrent year twig thickness: thickWood specific gravity: unknown

CultureLight requirement: full sun

Soil tolerances: clay; sand; loam; acidic; occasionally wet; well-drainedDrought tolerance: highAerosol salt tolerance: unknown

OtherRoots: not a problemWinter interest: noOutstanding tree: noOzone sensitivity: unknownVerticillium wilt susceptibility: resistantPest resistance: resistant to pests/diseases

Use and ManagementBlue Japanese oak has been used as a street and parking lot tree in parts of the southeast for a number of years. Was used in USDA hardiness zone 7b until the 1983 freeze which reduced large trees to a collection of sprouts. It ap-pears to be tolerant of drought and poor, clay soil including those which are poorly-drained and grows well in tight soil spaces. Its tight crown lends a formal feel to the landscape.

Many upright trunks and branches originate from one point on the trunk without initial training, and this struc-ture could lead to a weak tree. Following initial training and pruning to develop a central leader and well-spaced branches, little care should be needed to maintain this tree. It should be grown and planted more in urban areas in the South.

Blue Japanese oak should be grown in full sun. It is tolerant of a wide range of soils, including heavy clay soils.

Propagation is by seed.

Pests and DiseasesThere is a large number of potential problems on oaks, but none of major concern.

Figure 3. Foliage