Oregon white oak
FS-189
QUERCUS
(oaks)
Oaks (Quercus) are the most important and
most widespread hardwood trees in the north tem­
perate zone, with about 300 species, including some
shrubs. More than 500 have been named, but many
probably are varieties or hybrids. Oaks are wide­
spread across North America and Eurasia, extend­
ing south in tropical mountains to Cuba, Colombia,
northern Africa, and Indonesia. The United
States has about 58 of tree size and perhaps 10
more of shrub size. Twenty of the native tree
species are considered important in management of
forest stands.
The oaks are deciduous or evergreen. Winter
buds, clustered at the ends of twigs, are composed
of many overlapping scales. The short-petioled
leaves are alternate in 5 rows, and are of various
shapes, lobed, toothed, or entire, thin or leathery,
mostly with prominent veins.
Minute flowers are borne in early spring with
the leaves, mostly lateral, with male and female
flowers on the same tree (monoecious). Male
flowers are in clustered drooping, slender, yellow­
ish catkins and the female flowers solitary or few,
and greenish. The fruit is an acorn (nut), which
matures in 1 or 2 years and sheds soon afterwards
in autumn. The short-pointed acorn has a hard
shell, a cup of small overlapping scales, and a seed,
usually bitter.
The native oaks are classified into 2 subgenera.
Red or black oaks (subgenus Erytkrobalanus)
have leaves with apex and lobes bristle-tipped,
acorns maturing the second year, bark usually
blackish and furrowed, and heartwood porous with
vessels open. White oaks (subgenus Quemus or
Lepidobalanus) have leaves with apex and lobes
not bristle-tipped, acorns maturing the first year,
bark usually light gray and scaly, and heartwood
less porous with vessels closed by outgrowths
(tyloses).
F-490720
596
AGRICULTURE HANDBOOK NO. 271
OREGON WHITE OAK (Quercus garryana Dougl.) Other common names: Garry oak, Oregon oak, post oak, Pacific post oak, white oak, prairie oak,
western oak, western white oak.
Oregon white oak grows from British Columbia
to the mountains along the central coast of Cali­
fornia. In British Columbia, it grows in a narrow
belt on the south and east coast of Vancouver
Island as far north as the Courtenay Valley, and
on islands adjacent to the east shore. It is local
ill the Fraser Valley. The range extends south­
ward through Washington and Oregon, generally
east of the summit of the Coast Range and west
of the summit of the Cascades. However, the
tree grows on the east side of the Cascades in the
Yakima and Tygh River Valleys, and in the Siski­
you Mountains in southern Oregon. In a few in­
stances it is found nearly to the coast in the valleys
of larger streams of the Coast Range. In Cali­
fornia, it is found at elevations up to 4,000 feet,
principally in the Siskiyou Mountains and the
drier parts of the Coast Range as far south as the
Santa Cruz Mountains, and, rarely, ill the Sierra
Nevada Mountaills (2) .'
well-drained slopes that are hot and dry in sum­
mer, but it reaches optimum development in the
deep loams of the Cowlitz and Lewis River Valleys
in southwestern Washington and the Willamette
Valley ill northwestern Oregon. Stumps 6 feet
HABITAT CONDITIONS
Climate
The humid zone of the Pacific Coast corresponds
roughly to the range of Oregon white oak. The
tree occupies sites where available soil moisture
is between that supporting grass or ponderosa pille
and the greater amount supporting Douglas-fir.
Climatic records emphasize the small variation of
seasonal precipitation in Oregon white oak's na­
tural habitat (table 1).
The geographic range of Oregon white oak lies
within the 25- to 40-inch zone of average annual
precipitation. Its range is more exactly delinea­
ted, however, by the growing season rainfall, April
through September, which averages from 4 to 10
inches. Oregon white oak might grow well on
sites with more moisture, but there it could not
compete with the faster-growing Douglas-fir.
Low temperatures, early and lafo frosts, and snow­
fall probably are not limiting to Oregon white oak,
because it survives them without serious damage.
Soils and Topography
Oregon white oak grows in soils that vary in
texture from stony and gravelly to heavy clay
( 6) .' The tree is common on grassy, stony,
1 Italic numbers in parentheses refer to Literature Cited,
p. 598.
:i Forbes, Robert H.
Oregon dendrology.
School of
Forestry, Oreg. State Col. 1945.
(Mimeographed rpt.)
F-506649
The range of Oregon white oak.
597
SILVICS OF FOREST TREES OF THE UNITED STATES
TABLE 1.-0limatologwal data for locations within the range of Oregon white oak
Location
Brttish Columbia:
Nanaimo_ _ _ _ _ _ _- __________
Victoria_____________---- ­ Washington:
Seattle__________-- - - - _ - -- Vancouver______ ___________
Oregon:
Corvallis__________________
Roseburg__________________
California:
Weaverville________________
Ukiah_____________________
Elevation
Feet
Temperature
Average precipitation
AbS'olute
Average
AprilSeptemher
Annual
Inches
Inches
Annual
o
F.
January
o
F.
July
o
F.
Maximum
o
Minimum
F.
o
Average
annual
frostfree
period
F.
Daus
125
210
7
4
36
27
14
100
7
8
32
37
53
52
40
38
63
67
98
103
3
-10
255
226
205
505
6
6
39
30
52
53
39
41
66
67
106
107
-14
-6
191
234
2,050
650
5
4
36
35
56
58
37
45
71
72
116
114
-5
12
118
208
m diameter have been noted on Sauvies Island
in the Columbia River near Portland, Oreg.
Oregon white oak is often found in pure groves on
both level and rolling agricultural land of all soils
found in major valleys of the Pacific Northwest.
But more often it occurs in groups or individually
on less fertile fringes of agricultural soils.
Oregon white oak occurs from low elevations iu
British Columbia to elevations of 3,800 feet in
Oregon, and at more than 4,000 feet in a few
places in California. Over much of its range it
grows on the poorer forest sites, southwest slopes,
and areas with thin soils and frequent rock out­
croppmgs.
This oak is commonly found on dry sites within
the general range of the typical variety of
Douglas-fir. These include valleys in the rain
shadow of the Coast Ranges, dry southerly slopes,
areas of gravelly soils, and table lands.
Associated Trees
Oregon 'vhite oak occurs to some extent in pure,
dense stands in the open valleys between the Coast
and Cascade Ranges forming the Oregon White
Oak Type (Type 233). In parts of westem
VVashingto11, 'vestern Oregon, and California, it
frequently forms an oak savanna 'vl1ere the forest
meets valley grasslands. Elsewhere, it merges
mto several forest types through complex
transitions.
It is a component of the Oak-Madrone Type
(Type 234), which covers about 400,000 acres in
Oregon and Washington. Commercial stands of
trees occupy only a small part of this acreage; the
majority is noncommercial scmb oak. In south­
ern Oregon, California black oak replaces Oregon
50
50
37
39
65
60
100+
95+
-10
0
----- ­
---- - ­
-
-
-
-
white oak as the principal tree of the Oak­
Madrone Type. Oregon white oak is also com­
mon in four other types: Pacific Ponderosa
Pine-Douglas-fir (Type 244), Pacific Douglas­
fir (Type 229), California Black Oak (Type 246),
and Digger Pine-Oak (Type 250).
Oregon 'vhite oak's most common associate is
Douglas-fir, which often comes in as an under­
story if the oak stand is not dense. The fir
quickly overtops the oak and frequently shades it
out. Other associated trees include Pacific
madrone, ponderosa pine, bigleaf maple, Oregon
ash, Pacific dogwood, tanoak, California black oak,
and California-laurel.
LIFE HISTORY
Reproduction and Early Growth
Flowering, seed production, mnd dissemina­
tion. Fiowering of Oregon white oak occurs dur­
ing April and May, usually later than Douglas-fir
and bigleaf maple.
Large crops of acorns are produced only every
few years, but the reasons for the periodicity of
seed crops are not known.
Acorns mature in one season and fall in Septem­
ber or October. The heavy acorns are usually
dispersed within a short distance of the tree. Ani­
mals that gather and store the acorns are believed
to be responsible for dissemination for any
distance.
During development, Oregon 'vhite oak acorns
are attacked by the filbertworm ( M elissopi,ts lati­
ferreanus) and the filbert weevil ( CurcUlio uni­
formis), The acorns are a preferred food of
pocket gophers, black-tailed deer, mice, chip­
-
598
AGRICULTURE
HANDBOOK NO.
munks, and squirrels. During some years the
entire crop is eaten.
Seedling development. Although large acorn
crops are produced every fe,v years, natural repro­
duction by seed is usually scarce, partly because of
the inability of the radicle to' penetrate the heavy
sod on which the acorns frequently fall.
The best natural seedbed for Oregon white oak
is moist soil covered \Vith an inch or more of leaf
litter. Germination is hypogeous, and the seed
requires no pretreatment to <break dormancy.
Germination occurs in the late foll or early spring,
and the germination percent usually is l1igh. The
juvenile root penetrates moist fr1ineral soil quickly
and deeply, but seedlings sometimes succumb to
moisture shortage in the summer. Competition
from plants, grazing, trampling, and grass fires
also cause deaths ( 5).
Height growth, except in the seedling stage, is
slo\v. Tolerance to shade is· greater in its youth
than at maturity (5).
Vegetative reproduction Vegetative propaga­
tion of all oaks is considered difficult; and no
instances of layering, rooting of cuttings, or graft­
ing have been reported for Oregon white oak.
Grafting has been successful on many white oaks
(4) and vegetative propagation of Oregon white
oak by this means appears to be possible. Stumps
of Oregon white oak sprout vigorously and pro­
vide the surest means of natural regeneration.
-
.-
Sapling Stage to Maturity
Growth and y ield. Growth from the sapling
stage to maturity is very slow. At best, the trees
do not reach 100 feet in height; they seldom aver­
age more than 70 feet on the best sites in a life
span that may last 500 years. Diameters at 250
years old are seldom more than 3 feet.
Volumes per acre in pure stands at various ages
and sites are not known. An 80-year-old stand
containing 160 trees 3.6 inches and larger in diam­
eter at breast height per acre was estimated to
have a volume of about 15 cords per acre.
Reaction to compe tition. Relative tolerance of
Oregon white oak is intermediate (1), but the tree
is also considered intolerant by some.' It usually
dies quickly when overto_pped by Douglas-fir,
although some trees have hved for 20 years after
being overtopped (5).
The tree is usually subclimax, becoming climax
only ?n ry, rocky southerl:y exposures. The pres­
ent d1stribut10n of stands m the Willamette Val­
ley indicates that Douglas- r has generally in­
vaded sites prev10".sly occupied by Oregon white
oak. Some extens10n of oak stands into valley
grasslands is also apparent (3).
-
-
J_i
3
Keniston, R. Personal communication.
Univ., Corvallis, Oreg. 195£.
Oreg.
State
271
Principal enemies.-Oregon
white oak is dam­
The western oak looper
(Lambdina fiscellaria somniaria) may defoliate it,
but usually causes no permanent damage. The
California tent caterpillar (M alacosoma califomi­
oum) and the blue-sided tent caterpillar (ill. con­
stricta) also are defoliators. Numerous cynipids
(gall wasps) attack the twigs and leaves of white
oak, each causing galls of characteristic sizes and
shapes. Some cause conspicuous twig killing by
forming masses of galls between the bark and the
'vood, thus blocking circulation. However, none
of the insect pests of this oak are considered seri­
ous, and the killing of Oregon white oak by insects
is probably uncommon.
The fungi attacking Oregon white oak includes
31 species. Of these, all but six are saprophytic.'
A pest that is common south of latitude 45 °20',
but rare or absent farther north, is the hairy mis­
tletoe (Phoradendron villosum), which inhibits
growth and sometimes kills the tree. The two
major decay fungi are shoestring root rot, Armil­
laria mellea, and a trunk rot, Polyporus dryophi­
lus. Oak mildew, Microsphaera alni, is a common
foliage disease.
aged by many insects.
RACES AND HYBRIDS
Quercus
( Q. douglasii X garryana) ; Q. subaon­
vexa ( Q. durata X Q. garryana) ; and Quercus
X howellii ( Q. dwmosa X Q. garryana) ( 7).
Racial variations include a shrublike form o f Quer­
CU$ garryana found on the shores and isl ands of
Three natural hybrids are reported:
X eplingii
Puget Sound and in an area near Klamath Falls,
Oreg. Acorns and leaves of Brewer oak (Q. oer­
stediana), a small to large spreading shrub occur­
ring on the west slopes of the Sierra Mountains in
California, are similar to those of Oregon white
oak. It has been described as a variety of Q.
garryana, but it also is considered a distinct species.
Revised from "Silvioal Oharacterifstics of Oregon White
Oak," by Roy R. Silen. U.S. Forest Serv. Pacific North­
west Forest and Range Expt. Sta. Silvieal Ser. 10, 13 pp.
1958,
LITERATURE CITED
(1) Baker, Frederick S.
1949. A revised tolerance table. Jo-ur. Forestry 47:
179-181.
(2) Bo\verman, l\L L.
1944. 'I'he :flowering plants and ferns of Mount
Diahlo, California. 290 pp. Gillick Press,
Berkeley, Calif.
4 Wright, E., and Childs, T. Personal communication.
Pacific Northwest Forest and Range Expt. Sta., Portland,
Oreg. 1956.
599
SILVICS OF FOREST TREES OF THE UNITED STATES
(6) Tarrant, Robert F.
(3) Habeck, James R.
1961. The original vegetation of the Mid-Willam­
ette Valley. Northwest Sci. 35: 65--67.
( 4) lrgens-Moller, H.
19!'\5. Forest-tree
1956. Forest soils of the Pacific North\Vest.
Amer. Foresters Proc. 1955: 73-76.
Soc.
(7) Tucker, John.M.
genetics
research:
Quercus L.
Econ. Bot. 9: 53-71.
(5) McCulloch, W. F.
1940. Oregon oak-tree of conflict.
46 (6) : 264--266, 286, 2SS.
Amer. Forests
1953. Two new oak hybrids from California.
drofio 12: 119--1 27.
(8) Whitford, H. N., and Craig, R. D.
1918. Forests of British Columbia.
serv. Cornn., 409 pp. Ottawa.
Ma­
Canad. Con­