garry oak, oregon oak, brewer oak

This information was originally published in Hardwoods of the Pacific Northwest, S.S. Niemiec, G.R. Ahrens, S. Willits, and D.E. Hibbs. 1995. Research Contribution 8. Oregon State University, Forest Research Laboratory

General Characteristics

Oregon white oak, a member of the beech family (Fagaceae), is one of only four deciduous oaks native to the West Coast. The massive, branching trunks and broad crowns of old white oaks are characteristic features of valley woodlands in the Pacific Northwest.

Size, Longevity, and Form

Mature Oregon white oaks are 50 to 90 ft tall (120 ft maximum) and 24 to 40 in. in DBH (97 in. maximum). Oregon white oaks may live 500 years. In forest stands on good sites, Oregon white oaks develop narrow crowns with small branches on straight, clear stems.

In more open stands and on poor sites, boles are typically short and crooked; shrubby stands of stunted trees are common. Open-grown trees develop very broad, rounded crowns (crown width may equal total height) with massive, crooked branches on short, massive boles. The root system of this species is composed of a deep taproot and well-developed laterals.

Geographic Range

Oregon white oak has a wide latitudinal range from Vancouver Island (lat 49° N) to southern California (lat 34° N), although it takes on a shrub form toward the southern end of this range. It is well distributed throughout the valleys west of the Cascade Range and Sierra Nevada on inland slopes of the Coast ranges.

Timber Inventory

A substantial inventory of Oregon white oak (450 MMCF) is distributed throughout western Oregon and northwestern California. A much smaller volume (13 MMCF) occurs in western Washington (Appendix 1, Table 1).

Biology and Management

Tolerance, Crown Position

Oregon white oak is generally intolerant, although this depends on the environment and associated vegetation. Sparse development of branches in closed stands indicates intolerance to shade. Although it can reproduce in its own shade, Oregon white oak will die after overtopping by Douglas-fir.

Ecological Role

Oregon white oak is a persistent climax or sub-climax species on dry sites or under regimes of periodic fire. Large oaks have thick bark and are resistant to fire. Smaller trees are generally killed or badly injured by fire. Oregon white oak is an early successional species on better sites, where it is replaced by Douglas-fir and bigleaf maple in the absence of fire. Historically, periodic fires were a major factor maintaining Oregon white oak woodlands. After a century of fire exclusion, many acres have progressed from open Oregon white oak, to closed white oak, to Douglas-fir. Fire prevention is probably causing continued decline in the extent of Oregon white oak type forests. The white oak type will continue to diminish without periodic fire.

Associated Vegetation

Many distinct Oregon white oak associations are recognized. Common associate trees of Oregon white oak are Douglas-fir, grand fir, ponderosa pine, bigleaf maple, Pacific madrone, California black oak, Oregon ash, and cherry. Common shrubs include hazel, hawthorn, snowberry, serviceberry, poison-oak, wild rose, and oceanspray. Herbaceous associates include many different grasses, western swordfern, western bracken, wild strawberry, bedstraw, and sweetroot. A great variety of other plant species grow with Oregon white oak in other forest types.

Suitability and Productivity of Sites

Oregon white oak is particularly suited to exposed, droughty sites at the margins of more productive forest land. It is also well suited for areas near rivers that are very wet in winter but droughty in the summer. Oregon white oak will grow well on better sites, but requires management to persist among more competitive Douglas-fir and maple.

The capability of a site for growing Oregon white oak should be evaluated by examining growth and form of older trees. Good potential for growth of this species is indicated by the following site characteristics:

Top height on mature trees of at least 60 ft

Sustained height growth of 1 to 2 ft per year for trees 10 to 30 years old

Continuing diameter growth on mature trees.

Climate

Oregon white oak grows across a diverse range of climates, most of which have moderate to extreme summer drought and annual precipitation of 10 to 100 in. Within its range, mean daily temperatures may vary from lows of 13 to 50 "F in January to highs of 60 to 84°F in July.

Oregon white oaks are well adapted to hot, dry conditions. With adequate moisture early in the season, relatively large trees may develop on sites where severe summer drought limits other species. Extensive stands of small, shrubby white oak, often mixed with Pacific madrone, grow on sites that are often too dry to support any other tree species.

Of the western hardwoods, Oregon white oak is one of the most resistant to damage from ice and snow. Twigs and buds have moderate resistance to cold injury. Healthy Oregon white oak are not prone to windthrow or breakage.

Elevation

Oregon white oak is usually found at lower elevations in the interior valleys. It grows from sea level to 3800 ft in the north and at elevations of up to 7500 ft at the southern end of its range.

Soils

While common on droughty soils, Oregon white oak is also competitive on soils that are poorly drained during the wet season and droughty during the summer. This commonly occurs on heavy clays, coarse-textured flood plains, and river terraces in the interior valleys. Oregon ash is also common under these conditions.

Flowering & Fruiting

The age at which Oregon white oak first produces seed has not been determined. Oregon white oak flowers appear with new foliage in spring. Oregon white oak usually flowers later than common associates, in March in the south, and June in the north. Separate male and female flowers grow on the same tree. Male flowers (greenish-yellow catkins) emerge from existing buds and at the base of new shoots, expanding to a size of 1.2 to 3.9 in. when fully developed. Small, red female flowers appear in the axils of new leaves. The acorns ripen from August to November during the first season after flowering.

Seed

Oregon white oak has large acorns, which are about 1.2 in. long and half as wide, and average 85 seeds/lb. Acorns should be collected from September to November. They must be kept cool and moist until germination. Although germination usually occurs in spring, seeds will germinate soon after dispersal under warm, moist conditions; they also germinate prematurely in cool, moist storage. As with other Oregon white oaks, sowing seeds in the fall may be best. Limited tests indicate rates of viability that are greater than 75 percent. Seeds remain viable for only one season.

Regeneration from Seed

Natural regeneration from seed is often quite good where there has been soil disturbance, particularly in the absence of fire or grazing. Seedlings rapidly develop a deep taproot, which may account for their ability to establish in grass and in droughty soils. The shoot of natural seedlings often remains small and shrubby for many years, perhaps to accommodate development of deep roots. This is followed by a sapling stage with relatively rapid growth. Regeneration from seed is greatly improved when seeds are protected from rodents and other predators.

Regeneration from Vegetative Sprouts

Oregon white oak sprouts vigorously after cutting or fire. Sprouts arise from dormant buds at the root collar and along the trunk. Both the vigor and the abundance of sprouts increase as the size of the parent tree increases. Stumps should be cut low to the ground in order to produce well-formed sprouts of good quality.

Regeneration from Planting

Nursery culture of Oregon white oak is relatively easy. Experience with other white oaks indicates that with vigorous nursery stock, Oregon white oak has good potential for management in plantations. Performance of Oregon white oak has been poor to fair in limited outplanting trials, however. There are no known examples of operational forest plantations.

Site Preparation and Vegetative Management

Cultivated seedlings of Oregon white oak grow rapidly and do not display the prolonged shrub stage observed for many wild seedlings. This suggests that site preparation and control of competition from grasses and shrubs could greatly improve growth of Oregon white oak seedlings in the field.

Stand Management

Oregon white oak has not been extensively managed for timber production. It shows good potential for management in closed, even-aged stands, as indicated by the relatively good stand growth and high stem quality in closed stands established after the exclusion of fire. Thinning in dense, sapling-sized stands can increase diameter growth.

Mixed-species Stands

Competitive associates such as Douglas-fir and bigleaf maple must be controlled to maintain Oregon white oak on better sites.

Growth and Yield

Growth of Oregon white oak is generally slow. Height growth is usually less than 1 ft per year and diameter growth is often 15 to 20 rings/in. Faster growth, particularly in diameter, is possible (3 to 10 rings/in.). Stump sprouts may grow as much as 3 ft per year during the first 3 years. Oregon white oak stands may achieve basal area of up to 265 ft2 per acre and volume as high as 4500 ft3 per acre.

Interactions with Wildlife

Oregon white oak trees and stands are very important for wildlife. Oak woodlands and forests provide food and habitat for many species. Two of note are the acorn woodpecker and Merriam’s wild turkey. Diversity of bird species is often higher in oak forests than in adjacent conifer forests. Both acorns and foliage provide high-protein food for many animals.

Insects and Diseases

Filbertworm (Melissopus latiferreanus) and filbert weevils (Curculio occidentalis) attack acorns of Oregon white oak. Hundreds of other insect species live on Oregon white oaks, although few cause significant damage. The most damaging insect is the western oak looper (Lambdina fiscellaria somniaria), which can defoliate trees over large areas; tent caterpillars also have a preference for oak. Gall wasps are common on Oregon white oak. Noticeable damage is often inflicted on oak by Bassettia ligni, which girdles and kills branches.

Numerous pathogens attack Oregon white oak. The hairy mistletoe is widespread. Shoestring root rot, Armillaria ostoyae (A. mellea), and white pocket rot and butt rot (Polyporus dryophilus) cause significant damage. One episode of anthracnose disease (Gnomonia quericina) appeared to cause significant damage in Washington in 1968.

Genetics

Oregon white oak hybridizes with four other oaks in California. There is relatively little genetic variation within the species, despite its wide latitudinal range.

Harvesting and Utilization

Cruising and Harvesting

Diameter at breast height and total height can be used with tables or equations to estimate total tree volume in cubic feet and sawlog volume. Log or tree grades are not used for Oregon white oak; however, recent studies have shown that there are differences in the value of lumber that can be recovered from each of the log grades. Log grades developed for eastern hardwoods may be a useful marketing tool in the future. Oregon white oak logs check easily during storage and should be end-coated to prevent splits.

Product Recovery

Sawlogs usually have a minimum small-end diameter of 8 in., smaller logs are chipped for pulp. Rot, checks, and cross-grain have been problems in the lumber.

There is increasing interest in using Oregon white oak for cooperage for wine barrels, flooring, and chairs. It has been used for pulp and is frequently used for firewood.

Wood Properties

Characteristics

Oregon white oak is a hard, heavy wood that has distinct growth rings and very prominent rays. The sapwood is whitish to light brown; the heartwood is a pale, yellowish, grey-brown, often with a slight greenish cast. The dry wood is has no characteristic odor or taste. Oregon white oak is ring porous; the earlywood pores are large and distinct, forming a conspicuous band with each growth ring. The latewood pores are small and numerous, and require a hand lens to view. Rays are of two types, broad and narrow. The broad rays are readily visible to the naked eye and are separated by several to many narrow rays. When oaks are quartersawn, these rays appear as a pronounced fleck. The earlywood pores are plugged with a membranous growth known as tyloses, which makes the wood impenetrable to fluids. For commercial purposes, Oregon white oak is classed with the other white oaks in USDA Forest Service nomenclature.

Weight

Oregon white oak weighs about 69 lb/ft3 when green and 50 lb/ft3 at 12 percent moisture content (MC). The average specific gravity is 0.72 (green) or 0.75 (ovendry).

Mechanical Properties

The wood of Oregon white oak has exceptional strength properties and is noted for its hardness, toughness, resiliency, and resistance to abrasion. It holds nails well, but, because of its density and hardness, will split without preboring. See Appendix 1, Table 3 for average mechanical properties for small clear specimens.

Drying and Shrinkage

Oregon white oak requires special care and attention to detail during an extended kiln schedule to properly reduce MC to a level suitable for interior products such as flooring, furniture, or millwork. Drying defects can cause serious downgrade. End- and surface-checking result from uncontrolled or overly rapid drying; honeycomb, collapse, and ring failure occur because of wetwood. Iron stains form when tannins contact certain metals, and grey sapwood staining will result if there is poor air circulation. Green MC of the wood is generally 67 to 72 percent (ovendry). Shrinkage values for green to ovendry (based on the original green size) average 4.2 percent radially and 9.0 percent tangentially. It is suggested that all the upper grades be air-dried to 20 percent MC and then kiln-dried according to a time schedule (See the table below for the appropriate kiln schedule).

Machining

Species in the white oak group, including Oregon white oak, generally machine well. They plane well (87 percent defect-free pieces), turn well (85 percent defect-free) and yield accurately sized, smooth-sided holes when bored and mortised. White oaks also bend exceptionally well after steaming. On white oak, sanding produces a smooth, relatively scratch-free surface with little or no fuzzing. The hardness, tannin content, and density of these woods cause considerable tool dulling and sandpaper wear. It is recommended that saws and other tools have hook angles of 15 to 20° and sharpness angles of 55° for optimum performance on white oaks. Care should be taken not to overfeed this wood or attempt to remove too much stock at once because machine burn or surface roughness may result.

Adhesives

Oregon white oak bonds satisfactorily, and there are no unusual problems when gluing conditions are well controlled. Careful curing/ drying of glue joints is required to prevent sunken gluelines from subsequent machining.

Finishing

All white oaks finish well, although it may be necessary to fill the grain. White oaks color best with dyes or transparent stains, especially if dramatic color changes are sought. Heavily pigmented stains can also be used if care is taken to remove excess pigment from the wood.

Durability

Oregon white oak heartwood is classified as resistant to decay. In tests conducted by staff of the OSU Forest Products Department, untreated fence posts lasted an average of 18 years before failure. The sapwood has no decay resistance and will deteriorate rapidly. Iron stain and oxidative stain sometimes occur on Oregon white oak.

Uses

Oregon white oak is used for furniture, flooring, railroad ties, tight cooperage, turnings, veneer (sliced), millwork, fence posts, mine timbers, handles, boxes, crates, pallets, caskets, pulp chips, and fuelwood.

Related Literature

COBLENTZ, B.E. 1980. Production of Oregon white oak Quercus garryana acorns in the Willamette Valley, Oregon utilization by deer. Wildlife Society, Bulletin 8:348-350.

EVANS, D. 1972. Alternate generations of gall cynipids (Hymenoptera:Cynipidae) on Garry oak. Canadian Entomologist 104:1805-1818.

GUMTOW-FARRIOR, D.L., and C.M. GUMTOW-FARRIOR. 1992. Managing Oregon white oak communities for wildlife in Oregon’s Willamette Valley: a problem analysis. Unpublished report prepared for the Oregon Department of Fish and Wildlife Nongame Program.

HIBBS, D.E., and B.J. YODER. 1993. Development of Oregon white oak seedlings. Northwest Science 67:30-36.

McDONALD, P.M., D. MINORE, and T. ATZET. 1983. Southwestern Oregon-northern California hardwoods. P. 29-32 in Silvicultural Systems for the Major Forest Types of the United States. R. Burns, tech compil. USDA Forest Service, Washington, DC. Agriculture Handbook 445.

PLUMB, T.R., and P.M. McDONALD. 1981. Oak management in California. USDA Forest Service, Pacific Southwest Forest and Range Experiment Station, Berkeley, California. General Technical Report PSW54. 12 p.

RIEGEL, G.M., B.G. SMITH, and J.F. FRANKLIN. 1992. Foothill oak woodlands of the interior valleys of southwestern Oregon. Northwest Science 66:66-76.

STEIN, W.I. 1990. Oregon white oak. P. 650-660 in Silvics of North America. Volume 2, Hardwoods. R.M. Burns and B.H. Honkala, USDA Forest Service, Washington D.C. Agriculture Handbook 654.