Quercus garryana Dougl. ex Hook.
Oregon White Oak
Fagaceae -- Beech family
William I. Stein
Oregon white oak (Quercus garryana), a broadleaved deciduous hardwood common inland along the Pacific Coast, has the longest north-south distribution among western oaks-from Vancouver Island, British Columbia, to southern California. It is the only native oak in British Columbia and Washington and the principal one in Oregon. Though commonly known as Garry oak in British Columbia, elsewhere it is usually called white oak, post oak, Oregon oak, Brewer oak, or shin oak. Its scientific name was chosen by David Douglas to honor Nicholas Garry, secretary and later deputy governor of the Hudson Bay Company.
The range of Oregon white oak spans more than 15° of latitude from just below the 50th parallel on Vancouver Island in Canada south nearly to latitude 34° N. in Los Angeles County, CA. South of Courtenay, BC, Oregon white oak is common in the eastern and southernmost parts of Vancouver Island and on adjacent smaller islands from near sea level up to 200 m (660 ft) or more (47). It is not found on the British Columbia mainland except for two disjunct stands in the Fraser River Valley (28). In Washington, it is abundant on islands in Puget Sound and distributed east and west of the Sound and then south and east to the Columbia River at elevations up to 1160 m (3,800 ft) (68). Oregon white oak is widespread at lower elevations in most of the Willamette, Umpqua, and Rogue River Valleys of western Oregon (67,68). It is also common in the Klamath Mountains and on inland slopes of the northern Coast Ranges in California to San Francisco Bay but infrequent from there southward to Santa Clara County (29).
In small tree and shrub sizes, Oregon white oak extends inland to just east of the Cascade Range, mainly in the Columbia River and Pit River drainages (29,50,67,68,71). It has a scattered distribution the entire length of the western Sierra Nevada south to the Tehachapi Mountains in Kern and northern Los Angeles Counties where it forms extensive brush fields at elevations up to 2290 m (7,500 ft) (29,76).
-The native range of Oregon white oak.
Oregon white oak grows in diverse climates, ranging from the cool, humid conditions near the coast to the hot, dry environments in inland valleys and foothill woodlands. Records from 48 climatic observation stations within or bordering its range indicate that Oregon white oak has endured temperature extremes of -34° to 47° C (-30° to 116° F) (45,47,53,77). Average annual temperatures range from 8° to 18° C (46° to 64° F); average temperatures in January, from -11° to 10° C (13° to 50° F); and in July, from 16° to 29° C (60° to 84° F).
Average annual precipitation ranges from 170 mm (6.7 in) at Ellensburg, WA, east of the Cascades to 2630 mm (103.5 in) at Cougar, WA, west of the Cascades. Precipitation at the southern end of the range of Oregon white oak (Tehachapi) averages 270 mm (10.6 in), similar to that at northerly locations east of the Cascades-Ellensburg, Yakima, and Goldendale in Washington and The Dalles and Dufur in Oregon. Average annual snowfall ranges from little, if any, at several locations to 417 cm (164 in) at Mineral in Tehama County, CA. Average precipitation in the growing season (April through September) ranges from 30 mm (1.2 in) at Tehachapi, CA, and Ellensburg, WA, to 630 mm (24.8 in) at Cougar, WA. Length of average frost-free season (above 0° C; 32° F) ranges from 63 days at Burney in Shasta County, CA, to 282 days at Victoria, BC.
Oregon white oak can grow on a wide variety of sites, but on good sites it is often crowded out by species that grow faster and taller. Hence, Oregon white oak is most common on sites that are too exposed or droughty for other tree species during at least part of the year, including inland valleys and foothills, south slopes, unglaciated and glaciated rocky ridges, and a narrow transition zone east of the Cascades between conifer forest and treeless, dissected plateau. Although usually considered a xeric species, Oregon white oak also commonly occurs in very moist locations-on flood plains, on heavy clay soils, and on river terraces. These locations appear to have two common characteristics-standing water or a shallow water table during a lengthy wet season and gravelly or heavy clay surface soils that probably are droughty during the extended dry season. The distribution of Oregon white oak gives evidence that it can withstand both lengthy flooding and drought.
Oregon white oak grows on soils of at least four orders: Alfisols, Inceptisols, Mollisols, and Ultisols. Specific soil series include Hugo and McMahon in coastal northern California and Goulding near Santa Rosa (75,78). In Oregon's Willamette Valley, Oregon white oak is found on soils derived from alluvial deposits (poorly drained gray brown Amity and Dayton series), sedimentary rocks (deep, welldrained brown Steiwer, Carlton, Peavine, Bellpine, Melbourne, and Willakenzie series), and basic igneous rocks (brown or reddish, moderately deep, well-drained Nekia, Dixonville, and Olympic series) (22,38,67,73). A subsurface clay layer that restricts water penetration is characteristic of soils in most of these series. White oak stands near Dufur in eastern Oregon grow in soils derived from basalt and andesite (32); in southern Oregon, they grow in soils derived from andesite, granite, and serpentine (79). On the southeastern tip of Vancouver Island, BC, seven soils supporting a vegetational sequence of grass, Oregon white oak, and Douglas-fir were gravelly loams or gravelly sandy loams that developed on young, nonhomogeneous parent materials (11).
Soils under Oregon white oak stands are generally acidic, ranging in pH from 4.8 to 5.9 (11,75,78). Bulk densities ranging from 0.61 to 1.45 have been measured (73,78). Many white oak stands grow on gentle topography; only one-fourth of those examined in the Willamette Valley were on slopes greater than 30 percent (73).
Oregon white oak is found in pure, closed-canopy stands; in mixture with conifers or broad-leaved trees; and as scattered single trees or groves on farmlands, woodlands, and prairies. It grows to large sizes but is also found extensively as scrub forest. The best stands are in western Oregon and Washington-in the Cowlitz, Lewis, and Willamette River drainages-but stands or trees with substantial volume are found from British Columbia to central California. Dense dwarf or shrub stands of Oregon white oak, earlier identified as Quercus garryana var. breweri, and other stands previously identified as Q. garryana var. semota, form dense thickets over large areas in California (29,35,57,76,81). Similar dwarf or shrub forms grow to a more limited extent on severe sites in the rest of its range (57,79).
Oregon white oak is recognized as a distinct forest cover type (Society of American Foresters Type 233) and is listed as an associated species in at least eight other forest cover types (20): Pacific Douglas-Fir (Type 229), Port Orford-Cedar (Type 231), Redwood (Type 232), Douglas-Fir-Tanoak-Pacific Madrone (Type 234), Pacific Ponderosa Pine (Type 245), California Black Oak (Type 246), Knobcone Pine (Type 248), and Blue Oak-Digger Pine (Type 250). Its prominence and occurrence in these types, as well as in several others for which it is not specifically listed, vary widely.
Plant communities have been identified in parts of the Oregon white oak type. A Garry oak community of two types (oak parkland and scrub oak-rock outcrop), a Garry oak-arbutus, and an arbutus-Garry oak community have been defined in the Victoria, BC, metropolitan area (42). Four communities, ranked in order from wettest to driest, have been identified in white oak forests of the Willamette Valley: Oregon white oak/California hazel/western swordfern, Oregon white oak/sweet cherry/common snowberry, Oregon white oak/Saskatoon serviceberry/common snowberry, and Oregon white oak/Pacific poison-oak (73). These communities are floristically similar, being differentiated primarily by the relative coverage and frequency of a few shrub species. Five Oregon white oak communities identified in the North Umpqua Valley of Oregon were similar to the xeric Oregon white oak/Pacific poison-oak association of the Willamette Valley; a sixth was a riparian association dominated by Oregon white oak and Oregon ash (Fraxinus latifolia) (62). In California, four communities dominated by Oregon white oak were found in the Bald Hills woodlands of Redwood National Park (70) and three communities dominated by Oregon white oak or related hybrids were identified in a limited area on Bennett Mountain (75). The shin oak brush association, largely composed of Oregon white oak, is a distinctive plant community in Kern and Los Angeles Counties (76).
The composition of Oregon white oak communities varies greatly because of differences in soil, topography, and climate, and in fire and grazing histories. Because of proximity to farmlands, many communities include introduced forbs and grasses. Pacific poison-oak (Rhus diuersiloba) and common snowberry (Symphoricarpos albus) are probably the most widespread and characteristic shrub associates.
Species often found with Oregon white oak are listed in table 1. The listing is not exhaustive; it just indicates the great variety of common associates. Species associated with Oregon white oak in chaparral communities and on serpentine soils are listed in other sources (15,16,79).
|Abies grandis||Amorpha californica||Agropyron spicatum|
|Acer circinatum||Arctostaphylos columbiana||Agrostis spp.|
|Acer glabrum||Arctostaphylos manzanita||Allium spp.|
|Acer macrophyllum||Arctostaphylos media||Athysanus pusillus|
|Aesculus californica||Arctostaphylos uva-ursi||Avena barbata|
|Alnus rubra||Berberis aquifolium||Balsamorhiza deltoides|
|Amelanchier alnifolia||Berberis nervosa||Brodiaea spp.|
|Arbutus menziesii||Ceanothus cuneatus||Bromus spp.|
|Betula occidentalis||Ceanothus integerrimus||Camassia spp.|
|Castanopsis chrysophylla||Ceanothus velutinus||Carduus pycnocephalus|
|Cercocarpus betuloides||Cornus stolonifera||Carex spp.|
|Cornus nuttallii||Crataegus oxyacantha||Chlorogalum pomeridianum|
|Corylus cornuta||Cytisus scoparius||Collinsia spp.|
|Crataegus douglasii||Gaultheria shallon||Crocidium multicaule|
|Fraxinus latifolia||Hedera helix||Cynosurus echinatus|
|Heteromeles arbutifolia||Holodiscus discolor||Dactylis glomerata|
|Juniperus scopulorum||Osmaronia cerasiformis||Danthonia californica|
|Libocedrus decurrens||Philadelphus lewisii||Delphinium menziesii|
|Lithocarpus densiflorus||Physocarpus capitatus||Dentaria californica|
|Pinus contorta||Purshia tridentata||Dodecatheon hendersonii|
|Pinus monticola||Rhus diversiloba||Dryopteris arguta|
|Pinus ponderosa||Ribes sanguineum||Elymus glaucus|
|Pinus sabiniana||Rosa eglanteria||Eriogonum nudum|
|Populus tremuloides||Rosa gymnocarpa||Eriophyllum lanatum|
|Populus trichocarpa||Rosa nutkana||Erythronium oregonum|
|Prunus avium||Rubus laciniatus||Festuca spp.|
|Prunus emarginata||Rubus parviflorus||Fritillaria lanceolata|
|Prunus virginiana||Rubus procerus||Galium spp.|
|Pseudotsuga menziesii||Rubus ursinus||Holcus lanatus|
|Pyrus communis||Spiraea betulifolia||Hypericum perforatum|
|Pyrus fusca||Spiraea douglasii||Lathyrus spp.|
|Pyrus malus||Symphoricarpos albus||Lomatium utriculatum|
|Quercus agrifolia||Symphoricarpos mollis||Lonicera ciliosa|
|Quercus chrysolepis||Symphoricarpos rivularis||Lotus micranthus|
|Quercus douglasii||Vaccinium ovatum||Lupinus spp.|
|Quercus kelloggii||Vaccinium parvifolium||Melica geyeri|
|Rhamnus purshiana||Viburnum ellipticum||Mimulus spp.|
|Salix spp.||Montia spp.|
|Sambucus cerulea||Nemophila heterophylla|
|Taxus brevifolia||Osmorhiza spp.|
|Thuja plicata||Phacelia linearis|
|Tsuga heterophylla||Platyspermum scapigera|
|Umbellularia californica||Plectritis spp.|
¹ Sources: 4,10,11,13,20,22,24,28,31,32,35,42,47,54,62,63,67,69,70,71,72,73,75,78
Flowering and Fruiting- Oregon white oak flowers somewhat later in the spring than many of its associates. Flowering has been noted in March, April, May, and June (72,74), but the seasonal span is probably greater over the wide range of latitudes and elevations where this species occurs. Flowers appear concurrently with new leaves and extension of twig growth.
The species is monoecious, bearing slim, staminate flowers (catkins) that emerge from buds on existing twigs and also appear on the basal end of developing twigs (64). Some catkins associated with new twig growth just originate from the same bud; others are located as much as 5 mm (0.2 in) from the base on new growth. Catkins are pale yellow tinged with green. Fully extended catkins vary greatly in length-in one collection, from 3 to 10 cm (1.2 to 3.9 in). Catkins of the same twig and cluster are in various stages of development-some are fading before others reach full size. The faded dry catkin is light brown and fragile.
The closed pistillate flowers are small, deep red, and covered with whitish hairs (64). They appear in axils of developing leaves, either single and sessile or as many as five or six on a short stalk up to 2 cm (0.8 in) long. Two flowers are often located at the base of the stalk and several along and at its tip. Basal flowers may be open while others on the stalk are still tiny and tightly closed. Flower openings are narrow; the interior elements are greenish to yellowish. Flowers were found on new growth that had extended only 1 cm (0.4 in) or up to 12 cm (4.7 in); most flowers were on new growth 4 to 7 cm (1.6 to 2.8 in) long. Flowering appears at its fullest when the first leaves are about half size; when leaves approach full size, catkins are withered. On a single tree, flowering seems to be a short event, perhaps a week long, as leaves develop quickly once growth starts.
Individual trees are known to flower abundantly, but observations are needed on the regularity of flowering and on the variability within and between stands and locations.
Seed Production and Dissemination- Seed crops may be heavy but are considered irregular. The large acorns, typically about 3 em (1.2 in) long and half as wide, mature in one season and ripen from late August to November. The age when a tree first bears fruit, the age of maximum production, and the average quantity produced have not been determined. In one collecting effort, about 18 kg (40 lb) of acorns per hour could be hand-picked from the ground under woodland trees between Redding and Weaverville, CA. The yield was estimated to be 5 to 9 kg (10 to 20 lb) each for trees 3 to 9 in (10 to 30 ft) tall and 15 to 30 cm (6 to 12 in) in diameter; production for this fair crop was about 560 kg/ha (500 lb/acre) (81). Northeast of Mount Shasta, a fair crop the same year yielded about 23 kg (50 lb) of acorns from a single tree 8 in (25 ft) in height and crown spread. In the Willamette Valley, acorns were dispersed from September to November, and three crops ranged from failure to 1737 kg/ha (1,550 lb/acre) ovendry-weight basis (12). Large crops of acorns are also produced by shrubby forms of Oregon white oak, but density of the stands can make collection difficult.
The heavy seeds disseminate by gravity only short distances from the tree crowns, except on steep slopes. Local transport is attributed primarily to the food-gathering activities of animals. In the past, Indians-and also pigeons-may have been responsible for long-distance colonization of Oregon white oak (28,71).
Seedling Development- Acorns of Oregon white oak must be kept moist until they germinate. In nature, moisture is maintained by a layer of leaves or through shallow insertion into soil from impact, rodent activity, animal trampling, or other soil disturbances. A moisture content of 30 percent or more must be maintained in cool regulated storage to maintain seed viability. Storage conditions have not been determined specifically for Oregon white oak; several methods recommended for keeping seeds moist should be suitable (46,65).
The acorns are large and heavy, averaging about 5 g each (85/lb). Viability has been better than 75 percent in the few samples tested (46), but the usual quality of the seeds is unknown. The seeds are not dormant; they will germinate soon after dispersal if subjected to warm, moist conditions. They will also germinate prematurely in low-temperature stratification. Normally, seeds retain viability only until the next growing season; chances of extending the viability period have not been determined.
Seedlings of Oregon white oak generally appear in the spring. Germination is hypogeal, and the rapid development of a deep taproot is believed responsible for their ability to establish in grass. Shoot development is relatively slow but can be greatly accelerated with long photoperiods (43). Seedlings are not produced now for forest plantings, but raising them in containers is readily possible. Direct seeding of acorns should also prove successful if seeds and young seedlings are protected from rodents and other predators. In at least some circumstances, natural reproduction from seed seems to occur readily (13,28,35).
Vegetative Reproduction- Oregon white oak sprouts abundantly from dormant buds on cut stumps, root collars, and along exposed trunks. Sprouts provide the most certain way to obtain natural regeneration. In 3 years, stump sprouts in 49 clumps in northwestern California averaged 10 per clump; height of the tallest sprout averaged 2.8 in (9.2 ft) and crown diameter per clump 2.5 in (8.2 ft) (52). Larger stumps produced more sprouts, larger clumps, and faster growing shoots. The spread of Oregon white oak by root sprouts has been noted in widely separated instances (28,68,69,70,71,74). In general, the rooting or layering of oak cuttings is difficult, and there is no reason to believe that Oregon white oak would be easier to reproduce by these methods than other oaks.
Growth and Yield- Under favorable conditions, mature Oregon white oak trees are 15 to 27 in (50 to 90 ft) tall and 60 to 100 cm (24 to 40 in) in d.b.h. (34,48,72,73). A maximum height of 36.6 m (120 ft), crown spread of 38.4 in (126 ft), and diameter of 246 cm (97 in) at d.b.h. are on record (2,35). Typically, open-grown trees have short holes bearing very large, crooked branches that form dense, rounded crowns (fig. 3). Such trees occupy much space but do not produce much volume for commercial use, except for fuel. In contrast, forest-grown trees 70 to 90 years old have slim, straight holes, fine side branches, and narrow crowns (60). Trees measured in northwestern California had average form classes of 63 and 68 (34). Branchwood of trees over 60 cm (24 in) in d.b.h. averaged 24 percent of total cubic volume. Trees of better form are probably developing now because young stands are more even aged and better stocked than those in the past, but such stands are limited in extent and widely scattered.
Resource inventories of various intensities indicate that the Oregon white oak type occurs on at least 361 400 ha (893,000 acres) in California, Oregon, and Washington and, as a species, comprises 26.2 million in' (926 million ft') or more of growing stock (7,8,9,10,21,25,26,27). As a component of woodland and other vegetation types, Oregon white oak is found on an additional 299 100 ha (739,000 acres) in California and in sizeable, undefined areas in Oregon and Washington. In California, the mean stand growing-stock volume in the type was 76.9 m³/ha (1,099 ft³/acre), and the maximum found was 314.7 m³/ha (4,498 ft³/acre).
Oregon white oak generally grows slowly in both height and diameter, but there are exceptions. Limited data from widely separated locations indicate that six to eight rings per centimeter (16 to 20/in) is a common rate for slower growing Oregon white oaks (28,68,72,75). For example, trees in a full stand 47 to 70 years old on deep Willakenzie soil at Corvallis, OR, averaged 14 in (46 ft) in height, 15 cm (6.0 in) in d.b.h., and eight rings per centimeter (20/in) in radial growth (38). Oregon white oak has the capability, however, of growing faster than five rings per centimeter (13/in) (31,48,72,80). In the Cowlitz River Valley, the fastest rate shown on large stumps was 1.9/cm (4.9/in); in the Willamette Valley, the rate averaged 4.6/cm (11.8/in) for four forest-grown trees 95 to 135 years old that averaged 24 in (80 ft) tall and 48 cm (19 in) in d.b.h.
Basal area of Oregon white oak stands has ranged from 8.0 to 60.8 m² /ha (35 to 265 ft²/acre), with up to 19.3 m²/ha (84 ft²/acre) additional basal area of other species present. In these and other stands averaging 10 cm (4 in) or more in d.b.h., number of oak stems ranged from 10 to 2,800/ha (4 to 1,133/acre) (1,4,31, 62,69,70,72,75). Volumes for stands on different sites and of different ages are not known. One 80-year-old stand that averaged 160 trees 9 cm (3.6 in) and larger in d.b.h. would yield about 94.5 m³/ha (15 cords/acre) (60).
Rooting Habit- Oregon white oak has a deep taproot and a well-developed lateral system; it is very windfirm even in wet areas. Fast taproot extension and sparse development of laterals are shown by seedlings in the first few weeks of growth. Despite formation of a deep taproot, a high percentage of oak roots are found in upper soil layers. Only 11 percent of the total number of oak roots were found below 76 cm (30 in) in deep Willakenzie soil (38). In contrast, 28 percent of the total Douglas-fir roots in the same soil were found below 76 cm (30 in).
Reaction to Competition- Oregon white oak has been classed as intermediate in tolerance, intolerant, and very intolerant of shade (47). Perhaps such a range of tolerance best describes its status in different situations. Clearly, it is not tolerant of over-topping by Douglas-fir and associated conifers. Dead oaks often found beneath Douglas-fir canopies bear witness that they could not endure the shade (40,72). In some locations and situations, Oregon white oak perpetuates itself, indicating that it can reproduce adequately in its own shade. Branch development on open-grown trees may be very dense. Sparse development of side branches in closed stands provides evidence, however, that it should be classed as intolerant of shade.
Oregon white oak functions as both a seral and a climax species. It is long lived, reproduces from both seeds and sprouts, forms nearly pure stands, and can endure great adversities. In fact, it rates as a climax species because it has greater ability than other species to establish itself and persist where yearly or seasonal precipitation is sparse, where soils are shallow or droughty, or where fire is a repeated natural occurrence.
Geologic and floristic evidence indicates that Oregon white oak associations have evolved through successive eras as components of relatively and pine-oak forests, have repeatedly advanced northward from a locus in the southwestern United States and northwestern Mexico, and have repeatedly retreated as North American climates warmed and cooled (16). The most recent northward advance ended about 6,000 years ago; the more and vegetation types, including oak woodlands, are now being replaced by conifer forest favored by the climatic trend toward cooler and moister conditions.
The seral role of Oregon white oak is illustrated by major changes occurring in the Willamette Valley. Open oak woodlands, savannas dotted with oaks, and grasslands were prominent and widespread before the territory was settled; fires-natural as well as those set by Indians-maintained these open conditions (30,31,36,44,61). Post-settlement exclusion of fire permitted development of closed-canopy white oak stands that are typically of two ages-large spreading trees, now 270 to 330 years old, are scattered among smaller trees of narrow form, 60 to 150 years old (73). Where not restricted by agricultural practices, young oaks continue to encroach into grassland. But, in turn, many oak stands are being invaded and superseded by bigleaf maples or conifers, mainly Douglas-fir (fig. 4). A similar sequence of events is occurring in the northern oak woodland, a distinctive Oregon white oak type in California (5,51,69). Unless steps are taken to reverse present trends, the Oregon white oak type will continue to become a less prominent part of the western flora. A reduction in species diversity will also occur, for open-canopy communities have a more varied composition than closed conifer communities (13).
Damaging Agents- Because of their attractiveness as food, seed crops of Oregon white oak are often decimated quickly (12). Larvae of the filbertworm (Melissopus latiferreanus) and the filbert weevil (Curculio occidentalis) damage crops even before acorns ripen (23). Maturing or ripe acorns are consumed by woodpeckers, pigeons, doves, jays, wood ducks, mice, chipmunks, squirrels, pocket gophers, woodrats, deer, bear, and other wildlife, as well as by domestic animals.
Wind, wet snow, and freezing rain damage Oregon white oak less than associated hardwoods, but in tests it showed only moderate resistance to cold. Dormant buds collected northwest of Corvallis, OR, withstood -15° C (5° F) and twigs -20° C (-40 F) without injury (55).
Large Oregon white oaks are obviously fire resistant; they have withstood annual or periodic fires for years. But small oaks may be killed or badly damaged by fire, as evidenced by the increased density and spread of oak stands since the advent of fire control.
More than 110 pathogens have been found on the leaves, twigs, trunk, or roots of Oregon white oak (59). Most are of minor consequence; many are saprophytes. Leaf-spot, mildew, and anthracnose fungi sometimes attack the foliage, but control methods have been suggested for only one-an anthracnose disease (Gnomonia quercina). In 1968, this fungus caused moderate to severe dying of leaves and possibly death of oak trees in southern Pierce County, WA (14). Premature browning of foliage is occasionally widespread in the Willamette Valley, but the causes and effects have received only incidental attention. The hairy mistletoe is common on Oregon white oak in Oregon and California, forming conspicuous, rounded growths in the upper crown. Its effect on growth and vigor of this host is undetermined. The white pocket root and butt rot (Polyporus dryophilus) and the shoestring root rot (Armillaria mellea) are probably the most damaging rots found in Oregon white oak. Its heartwood is generally very durable; stumps and even relatively small stems may remain intact for years.
Although Oregon white oak is host to hundreds of insect species (19), damage is usually not severe, and loss of trees to insect attack is uncommon. The western oak looper (Lambdina fiscellaria somniaria) is probably the most damaging insect on white oak from Oregon north to British Columbia. In some years, oaks over large areas in the Willamette Valley are defoliated (23). The damage is temporary since the trees leaf out the next year and outbreaks are not sustained. The western tent caterpillar (Malacosoma californicum) and the Pacific tent caterpillar (M. constrictum) are widely distributed defoliators with a preference for oaks. Several species of aphid, particularly Teberculatus columbiae, feed on the underside of oak leaves; the snowy tree cricket (Oecanthus fultoni) lives in open-grown oaks and associated species; and several leafrollers (Abebaea cervella and Pandemis cerasana) are found on Oregon white oak. Oregon white oak is the principal host for R. cerasana, an introduced leafroller causing sporadic defoliation that is now maintaining a relatively high population and slowly extending its range around Victoria, BC (17). Many gall wasps are found on oaks; those prominent on Oregon white oak include Andricus californicus, which forms large, persistent, applelike galls on twigs; Bassettia ligni, which causes seedlike galls under the bark of branches that often girdle and kill the branch; Besbicus mirabilis, which forms mottled, spherical galls on the underside of leaves; and Neuroterus saltatorius, which forms mustard-seed-like galls on lower leaf surfaces that drop in the fall and jump around like Mexican jumping beans caused by activity of the enclosed larvae (18,23).
Only incidental damage by animals has been noted on vegetative parts of Oregon white oak. Douglas squirrels and western gray squirrels sometimes debark small branches infested by gall wasp larvae (64). Damage is scattered and may involve as much as one-fourth of a tree's crown. Gophers and other burrowing animals, which are abundant on forest borders, damage some roots. Livestock inflict some trampling and feeding damage on young oaks.
The wood of Oregon white oak is dense, with specific gravity ranging from 0.52 to 0.88 when ovendry (66), has moderate strength in static bending tests, but does not absorb shocks well (47). It rates high in compression and shear strength and is outstanding among 20 northwestern woods in tension and side hardness tests (47). The heartwood is at least as durable as that of white oak (Quercus alba) (58). Pallets made from Oregon white oak compare favorably in strength with those made from other species (66) and are higher in withdrawal resistance for nails or staples (41).
Specialty items, fenceposts, and fuel are now the primary uses of Oregon white oak. The wood is considered one of the best fuels for home heating and commands top prices. It has been used for flooring, interior finish, furniture, cooperage staves, cabinet stock, insulator pins, woodenware, novelties, baskets, handle stock, felling wedges, agricultural implements, vehicles, and ship construction (60). Consumption of Oregon white oak totaled 12 454 m³ (2,185,000 fbm) exclusive of fuel in 1910 but has since declined (60).
Although Oregon white oak is not grown commercially for landscape purposes, scattered native trees, groves, and open stands are highly valued scenic assets in wildland, farm, park, and urban areas (35,42,49,56). Mistletoe is a scenic growth on Oregon white oaks that is collected and sold as a decorative and festive minor product.
Until recent times, meal or mush made from acorns of many oaks (including Oregon white oak) was a common Indian food (35,71,81). When crops were heavy, white oak acorns were also gathered and stored by local ranchers for feed, mainly for hogs. Livestock forage for acorns and prefer those of white oaks to black oaks (81). The leaves have a protein content of 5 to 14 percent (35,56), and Oregon white oak is rated as good to fair browse for deer but poor for domestic livestock.
Oregon white oak woodlands and forests provide favorable habitat for wildlife (6) and also produce substantial amounts of forage for sheep and cattle (33). Infrequently, cattle are poisoned by foraging on oak; one instance involving Oregon white oak has been documented (37).
Oak-dominated forests in the western part of the Willamette Valley in Oregon have a higher diversity of birds in all seasons than adjacent conifer forests (3). Oregon white oak and ponderosa pine-Oregon white oak associations are preferred brood habitats for Merriam's wild turkey in south-central Washington (39).
Greenhouse experiments have shown that Oregon white oak is a good host for the gourmet truffle, Tuber melanosporum (43). The feasibility of managing Oregon white oak stands for truffle production, as many oak stands are managed in Europe, is being investigated.
Though Oregon white oak populations in Washington are disjunct and scattered, the chemical and morphological characteristics of their foliage are similar (71). Genetic differences appear so minor that seed distribution from a common source by Indians has been postulated. Ecotypic variation was observed in top and root growth of young seedlings from seed collections made from Corvallis, OR, southward (43). First-year seedlings from northern sources were taller and heavier.
Quercus garryana hybridizes naturally with four other oaks. Quercus x subconvexa Tucker (Q. durata x garryana), a small tree found in Santa Clara and Marin Counties, CA, is noteworthy because of its morphologically dissimilar parents-Q. garryana is a deciduous tree, Q. durata an evergreen shrub, and the hybrid is tardily deciduous (74). Quercus x howellii Tucker (Q. dumosa x garryana) is also a small tree found in Marin County and a hybrid between a deciduous tree and an evergreen or tardily deciduous shrub or tree. Quercus x eplingii C. H. Muller (Q. douglasii x garryana), a tree with deciduous leaves, is found in Lake and Sonoma Counties, CA (75). Hybrids between Q. garryana and Q. lobata are also found in Sonoma County (4).