BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Quercus garryana | Oregon White Oak 



GENERAL BOTANICAL CHARACTERISTICS : 
Oregon white oak is a drought-resistant, flood-tolerant, native,
monoecious, deciduous tree ranging from 25 to 90 feet (7.6-27 m) high,
and 24 to 40 inches (60-100 cm) in d.b.h.  Acorns are from 0.8 to 1.0
inch (0.6-2.5 cm) long.  Typically, the trunk supports stout, spreading
branches and a rounded crown.  The bark is thin and scaly. The root
system consists of a deep taproot and a well-developed lateral system,
making trees windfirm even in wet areas.  Oregon white oaks may live to
500 years of age [4,20,44,54].

Brewer oak grows from 3 to 16 feet (1-5 m) in height [30].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Sexual:  Oregon white oak is wind pollinated.  Acorns develop in 1 year.
Masts may be heavy but are irregular.  The age of sexual maturity, the
age of maximum production, and the average number of acorns produced
have not been reported.  Acorns are disseminated by gravity or animals.
Migrating band-tailed pigeons may disseminate acorns over great
distances [13].  Acorn predation is high; often the entire mast is
consumed [4].  Some acorns are buried by seed-caching scrub jays,
magpies, and various rodents.  The viability of fresh acorns has been
tested at 75 percent [39].  Fresh acorns germinate immediately under
warm, moist conditions.  Germination is hypogeal, with initial growth
concentrated on development of a taproot.  Shoot development is
relatively slow; seedlings take 10 years or more to attain 3.3 feet (1
m) in height [13,48].  Seedling survival is low in sod or heavy duff
[4].  It is speculated that exotic annual grasses outcompete Oregon oak
seedlings for water and light, but experimental results to date are
inconclusive [7].  Many seedlings are killed by browsing livestock,
deer, or rodents.  Pocket gopher frequently destroy young roots [13].

Vegetative:  Oregon white oak sprouts from the trunk and root crown
following cutting or burning.  Some sprouts that arise after burning
resemble rhizomes in appearance and growth habit. They originate from
the root crown and extend several meters before emerging from the humus
[41].  Sprouts grow rapidly; 3-year-old sprouts in Humbolt and Trinity
Counties, California, averaged 9.2 feet (2.8 m) in height [36].  The
sprouting ability of Oregon white oak declines with age.  Mature oaks
may be weak sprouters or fail to sprout altogether [25].


SITE CHARACTERISTICS : 
Soils and topography:  Oregon white oak can grow on a wide variety of
sites but is usually outcompeted on better sites.  It typically occurs
on poor, exposed or droughty locations such as inland valleys and
foothills or rocky ridges.  It also occurs on poorly drained areas with
a shallow water table or with standing water for part of the year.  Soil
texture is characteristically clay, but the oak grows in gravelly or
sandy loam as well.  Soil pH ranges from 4.8 to 5.9.  Slopes may be
steep but are typically gentle (less than 30 percent) [13].

Elevation:  Oregon white oak grows from sea level to 5,000 feet (1,524
m) in elevation [13,37].

Brewer oak grows from 3,000 to 7,500 feet (914-2,286 m) in elevation
[13,30].

Climate:  Oregon white oak grows in diverse climates, ranging from the
cool, humid conditions near the coast to the hot, dry environment of
inland valleys and foothill woodlands.  The species can endure
temperature extremes from -30 to 166 degrees Fahrenheit (-34 to 47 deg
C).  Average annual precipitation ranges from 103.5 inches (262 cm) at
Cougar, Washington to 10.6 inches (30 cm) in the Tehachapi Mountains of
California [13].

Plant associates:  Overstory associates not listed under DISTRIBUTION
AND OCCURRENCE include grand fir (Abies grandis), Pacific yew (Taxus
brevifolia), incense-cedar (Libocedrus decurrens), western redcedar
(Thuja plicata), California bay (Umbellularia californica), bigleaf
maple (Acer macrophyllum), river birch (Betula occidentalis), and tanoak
(Lithocarpus densiflorus) [11,13,50].

Shrub associates include over 50 species.  Some of these are manzanita
(Arctostaphylos spp.), buckbrush (Ceanothus cuneatus), English ivy
(Hedera helix), poison-oak (Toxicodendron diversilobum), thimbleberry
(Rubus parviflorus), California huckleberry (Vaccinium ovatum), and tall
Oregon-grape (Mahonia aquifolium) [13].

Ground cover associates are numerous.  They include bluebunch wheatgrass
(Pseudoroegneria spicata), springgold (Crocidium multicaule), California
toothwort (Dentaria californica), blue wildrye (Elymus glaucus),
threadleaf phacelia (Phacelia linearis), and Kentucky bluegrass (Poa
pratensis) [13].


SUCCESSIONAL STATUS : 
Oregon white oak is somewhat shade tolerant.  It can reproduce
adequately under its own shade but is intolerant of overtopping by
conifers [13].  Oregon white oakwoods are fire climax and are seral to
Douglas-fir (Pseudotsuga menziesii), grand fir, or redwood (Sequoia
sempervirens) forests in the absence of fire [16,27,28,49].  On xeric
sites unfavorable to conifers, Oregon white oak is considered a climax
species [20].


SEASONAL DEVELOPMENT : 
The following seasonal development was reported for Oregon white oak in
the Willamette Valley, Oregon [13]:

     catkins emerge:    March - June
     leaves emerge:     March - June
     stems lengthen:    March - June
     acorns ripen:      August - November
     acorns dispersed:  September - November
    

Related categories for Species: Quercus garryana | Oregon White Oak