Associated Forest Cover
provided by Silvics of North America
California-laurel is more commonly found in mixture with other
species than in pure stands. Choice pure stands were eliminated
when coastal and inland valleys were cleared for agriculture, and
only scattered groves and tracts of large mature trees
remain-many in parks or preserves (40). Pure stands of tall young
growth are also limited, but pure stands of shorter trees,
thickets, or prostrate mats are common on coastal bluffs, in
canyons, and elsewhere in California (19,24,35,61).
California-laurel is listed as an associated species in six forest
cover types: Port Orford-Cedar (Society of American Foresters
Type 231), Redwood (Type 232), Oregon White Oak (Type 233),
Douglas-fir-Tanoak-Pacific Madrone (Type 234), Canyon Live Oak
(Type 249), and California Coast Live Oak (Type 255) (13). Its
prominence in these types, as well as in several others for which
it is not specifically listed, varies widely.
Many trees, shrubs, and herbaceous plants are associated with
California-laurel in different parts of its extensive range
(table 1). The listing in table 1 is not exhaustive; it indicates
the variety of associated species. Usually, fewer species and
fewer individuals per species are found under the
California-laurel canopy than under the canopy of associated
trees, and the area bare of all vegetation is greater. In the
Coast Ranges south of San Francisco Bay, an average of 36 species
per site, mostly perennials, was found under the
California-laurel canopy, 55 species beneath the canopy of other
trees (61). Distances bare of vegetation along transects ranged
from 9 to 48 percent of the total under California-laurel, 0 to
10 percent under other trees. Where the laurel canopy is
particularly dense and extensive, understory vegetation may
almost be limited to mosses, ferns, and laurel seedlings (7,51).
Table 1- Trees, shrubs, and herbs associated
with California-laurel in different parts of its range¹
Trees
Shrubs
Herbs
Abies grandis
Adenostoma
fasiculatum
Actaea rubra
Acer circinatum
Amelanchier
spp.
Adiantum pedatum
Acer macrophyllum
Arctostaphylos
canescens
Antennaria
suffrutescens
Acer negundo
Arctostaphylos
columbiana
Arnica spathulata
Aesculus
californica
Arctostaphylos
hispidula
Aster radulinus
Alnus rhombifolia
Arctostaphylos
mariposa
Balsamorhiza
deltoides
Alnus
rubra
Arctostaphylos
nevadensis
Blechnum
spicant
Arbutus menziesii
Arctostaphylos
patula
Boykinia spp.
Castanopsis
chrysophylla
Arctostaphylos
tomentosa
Cheilanthes
siliquosa
Ceanothus
thyrsiflorus
Arctostaphylos
viscida
Chimaphila
umbellata
Cercis
occidentalis
Artemisia
californica
Chlorogalum
pomeridianum
Chamaecyparis
lawsoniana
Baccharis
pilularis
Convolvulus
polymorphus
Cornus nuttallii
Berberis spp.
Diplacus
aurantiacus
Corylus cornuta
Ceanothus spp.
Disporum spp.
Eucalyptus
globulus
Cornus californica
Dryopteris arguta
Fraxinus dipetala
Eriodictyon
californicum
Eriophyllum
lanatum
Fraxinus latifolia
Garrya buxifolia
Erythronium
oregonum
Garrya elliptica
Garrya fremontii
Fragaria
californica
Heteromeles
arbutifolia
Gaultheria shallon
Galium spp.
Libocedrus
decurrens
Holodiscus
discolor
Hieracium
cynoglossoides
Lithocarpus
densiflorus
Juniperus communis
Hierochloe
occidentalis
Myrica californica
Juniperus sibirica
Horkelia sericata
Picea sitchensis
Lonicera hispidula
Iris spp.
Pinus attenuata
Lotus scoparius
Juncus spp.
Pinus contorta
Lupinus albifrons
Linnaea borealis
Pinus coulteri
Myrica hartwegii
Lomatium spp.
Pinus jeffreyi
Pickeringia
montana
Lupinus nanus
Pinus lambertiana
Quercus dumosa
Marah fabaceus
Pinus monticola
Quercus durata
Mimulus guttatus
Pinus ponderosa
Quercus sadleriana
Osmorhiza
chilensis
Pinus sabiniana
Quercus
vaccinifolia
Oxalis oregana
Platanus racemosa
Rhamnus
californica
Pellaea mucronata
Populus
trichocarpa
Rhamnus crocea
Pityrogramma
triangularis
Prunus ificifolia
Rhododendron
californicum
Polypodium vulgare
Pseudotsuga
menziesii
Rhododendron
macrophyllum
Polystichum
munitum
Quercus agrifolia
Rhododendron
occidentale
Pteridium
aquilinum
Quercus
chrysolepis
Rhus diversiloba
Pyrola dentata
Quercus douglasii
Ribes spp.
Sanicula
crassicaulis
Quercus garryana
Rosa gymnocarpa
Satureja douglasii
Quercus kelloggii
Rubus laciniatus
Scrophularia
californica
Quercus lobata
Rubus parviflorus
Selaginella
bigelovii
Quercus wislizeni
Rubus procerus
Senecio bolanderi
Robinia
pseudoacacia
Rubus spectabilis
Smilacina stellata
Salix spp.
Rubus ursinus
Stachys rigida
Sambucus spp.
Rubus vitifolius
Synthyris
reniformis
Sequoia
sempervirens
Symphoricarpos
albus
Trientalis
latifolia
Taxus brevifolia
Symphoricarpos
mollis
Trillium ovatum
Thuja Plicata
Symphoricarpos
rivularis
Vicia spp.
Torreya
californica
Vaccinium spp.
Viola spp.
Tsuga heterophylla
Whipplea modesta
Xerophyllum tenax
¹Sources:
2,7,10,14,15,22,32,35,38,47,51,55,61,63
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Climate
provided by Silvics of North America
California-laurel grows in diverse climates, ranging from the
cool, humid conditions found in dense coastal forests to the hot,
dry atmospheres found inland in open woodlands and chaparral.
Records from 38 climatic observation stations within or bordering
its range indicate that California-laurel has endured temperature
extremes of -25° to 48° C (-13° to 118° F)
(41,46,59). Average annual temperatures range from 8° to 18°
C (46° to 64° F); average temperatures in January, from
-1° to 10° C (31° to 50° F); and in July,
from 13° to 29° C (56° to 84° F).
Average annual precipitation ranges from 338 mm (13.3 in) at Lemon
Cove in the southern Sierra Nevada to 2118 mm (83.4 in) at Gold
Beach by the mouth of the Rogue River in Oregon. Average annual
snowfall ranges from zero at some coastal locations to 742 em
(292 in) at Blue Canyon in Placer County, CA. Average
precipitation in the growing season (April through September)
ranges from 18 to 432 mm (0.7 to 17.0 in). Length of average
frost-free season (above 0° C or 32° F) ranges from 139
to 338 days. Clearly, California-laurel demonstrates broad
ecologic versatility.
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Damaging Agents
provided by Silvics of North America
Wind and snow cause appreciable
destruction and deformation in California-laurel stands. Blowdown
is common during severe wind and rain storms in California and
Oregon (24,51). Wet clinging snow abets windthrow, breaks tops,
and splits forks. Striking examples of crown deformation and
molding by strong winds are numerous near the coast.
Because of its thin bark, the tree is easily top-killed by fire,
but it sprouts rapidly. Dense clumps are often formed on cutover
land, which may prevent the establishment of desired conifers.
Very young California-laurel seedlings have less capacity than
dwarf chaparral broom (Baccharis pilularis) or coast live
oak (Quercus agrifolia) to resprout after complete
destruction by heat at ground level (34).
California-laurel is relatively tolerant to boron. In comparison
tests, it was less tolerant to boron than Digger pine (Pinus
sabiniana) but more tolerant than Pacific madrone (Arbutus
menziesii) or bigleaf maple (Acer macrophyllum) (18).
More than 40 species of fungi have been observed on
California-laurel, and perhaps three (Anthostoma oreodaphnes,
Nectria umbellulariae, and Sphaerella umbellulariae) are
restricted to this species (48). Few fungi cause serious damage
to the living tree. In central coastal California, a severe
outbreak of laurel leaf blight followed abnormally heavy
precipitation in two of three winters. A bacterium, Pseudomonas
lauracearum, and two fungi, Kabatiella phoradendri f.
sp. umbellulariae and Colletotrichum gloeosporioides,
were isolated from affected leaves (42). No trees were killed
and crowns leafed out anew the following year. Dieback of twigs
and new shoots was substantial, however, and was followed by
scattered dieback of branches up to 2.5 cm (1 in) in diameter
associated with a Botryosphaeria sp., a fungus
that has been blamed for much damage to this species (23).
Incidence of infection by endophytic fungi, primarily Septogloeum
sp., averaged 25 percent for leaf samples of
California-laurel collected from four sites representing an
environmental gradient in southwestern Oregon (44). Several sooty
molds and other diseases are found on laurel leaves; the stem
canker, Nectria galligena, occurs primarily where snow,
ice, or wind cause severe bending and cracks in the bark of stems
and branches; and Ganoderma applanatum fruits readily on
scarred trees.
Wood rot is common in California-laurel. Various fungi cause decay
associated with wounds, and G. applanatum may function as
a heart rot in live wood (23). Even in young stands, dead knots,
stem malformations, and root collars are often decayed. Cull in
one northern California study averaged 7 and 10 percent of the
gross cubic volume in trees of saw log or cordwood size and
quality, respectively (31).
California-laurel has no serious insect enemies. A leafblotch
miner (Lithocolletis umbellulariae), a stag beetle (Dichelonyx
valida), and a thrips (Thrips madronii) cause some
damage to leaves. The cottonycushion scale (Icerya purchasi)
used to be very damaging but is now under control (48).
Several wood borers and beetles attack dead parts of the tree;
but only the powderpost beetle (Ptilinus basalis) that
attacks dead and stored wood and oak bark beetles (Pseudopityophthorus
spp.) that infest injured, felled, and recently dead
trees cause damage of economic consequence (16).
Except for seed consumption, animal damage to California-laurel
appears minor. In some localities and situations, browsing damage
to seedlings and new sprout growth may be of consequence. Young
laurel seedlings are browsed less than some associated species
(34).
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Flowering and Fruiting
provided by Silvics of North America
California-laurel flowers
regularly and often profusely. The pale yellow, perfect flowers,
15 mm (0.6 in) in diameter, grow on short-stemmed umbels that
originate from leaf axils or near the terminal bud. Flower buds
develop early; those for the following year become prominent as
current-year fruits are maturing. Flowering within the long
north-south range of California-laurel has occurred in all months
from November to May, beginning before new leaves appear
(24,25,29,61). The flowering period may stretch into late spring
and summer by the occasional appearance of flowers originating in
axils of developing leaves (48). California-laurel flowers at an
early age; flowers have been observed on short whiplike shrubs
and on 1-year-old sucker growth that originated on a long broken
stub (50). Small insects appear to be the chief pollinators (25).
The fruits-acrid drupes each containing a single, thin-shelled,
nutlike seed 15 min (0.6 in) in diameter-ripen in the first
autumn after flowering (52). As drupes mature, their thin, fleshy
hull changes from medium green to speckled yellow-green, pale
yellow, or various other hues from yellow-green tinged with dull
red or purple through purplish brown to purple. Ripe drupes may
be yellow-green on one tree, dark purple on an adjacent tree
(11).
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Genetics
provided by Silvics of North America
Several racial variations are recognized. Umbellularia
californica forma pendula Rehd. is an uncommon,
broad-spreading tree distinctive for its pendulous branchlets
that contrast strongly with typically ascending branch growth
(24,45). Umbellularia californica var. fresnensis
Eastwood has fine white down on the lower surfaces of leaves
and on branches of the panicle (11). Gregarious, rockpile, dwarf,
and prostrate forms (24) may indicate other varietal differences.
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Growth and Yield
provided by Silvics of North America
Over much of its range,
California-laurel attains heights of 12 to 24 m (40 to 80 ft) and
diameters of 46 to 76 cm (18 to 30 in). On protected bottom lands
of southwestern Oregon and northern California, mature trees are
91 to 183 cm (36 to 72 in) in d.b.h. and 30 in (100 ft) or more
in height (20,24). A maximum d.b.h. of 404 cm (159 in) (1) and a
maximum height of 53.3 m (175 ft) have been reported (49).
California-laurel occurs as a noncontiguous forest type on about
76 080 ha (188,000 acres), 9 712 ha (24,000 acres) in Oregon and
66 368 ha (164,000 acres) in California (4,17). As a component of
conifer or other hardwood types, it occurs on an additional 437
060 ha (1,080,000 acres) in California and an undetermined
additional acreage in Oregon. Total growing stock volume is
approximately 14.7 million m³ (520 million ft³). In
California, the mean stand growing-stock volume in the type is
117 m³ per ha (1,677 W/acre), with a maximum of about 218 m³
per ha (3,125 W/acre).
The growth rate of California-laurel varies greatly because of the
many climatic, soil, and competitive conditions in which it
occurs. Several observers report its height growth is slow, about
0.3 in (1 ft) per year, but on good sites in southern Oregon,
height growth averages between 0.3 and 0.6 in (1 to 2 ft) per
year (3,12,51). Growth of trees from seed to 38 or 41 cm (15 or
16 in) diameter in 50 years has been reported (57). Total number
of stems 10 cm (4 in) in d.b.h. or larger in California and
Oregon stands with a large component of California-laurel ranged
from 245 to 2,402/ha (99 to 972/acre); reported basal areas
ranged from 34.0 to 167.4 m²/ha (148 to 729 ft²/acre)
(51,61,62).
Multiple trunks frequently develop in both opengrown and closed
stands of California-laurel. Trees in the open often attain a
crown spread greater than their height and may not develop a
well-defined upper trunk. Many forest-grown trees also fork
repeatedly; forking within 3 in (10 ft) of the ground is common.
Generally each fork grows vertically and side branches die.
Adjacent forked and unforked trees make similar height growth.
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Reaction to Competition
provided by Silvics of North America
California-laurel is generally
classed as shade tolerant, but the tolerance level is not well
defined. A very dense canopy is formed by its thick evergreen
leaves, which persist 2 to 6 years. The presence of many small
seedlings but no saplings under some closed canopies and the
development of long boles clear of live limbs indicate that
laurel is not always tolerant of its own shade. These indicators
are no criteria of tolerance relative to other species, however,
and laurel trees are common among moderately dense conifers.
In some localities, California-laurel appears to be the climax
vegetation (7,24,34,61). It is relatively long lived, reproduces
from both seeds and sprouts, forms dense pure canopies, and
appears to have few serious natural enemies. California-laurel
reproduces itself at natural light intensities of 1 to 5 percent
of full sunlight; the most dry weight in one experiment was
produced at 18 percent of full sunlight, but growth was also
reasonable at 8 percent (34,61).
Allelopathic influences have been suspected as the cause of more
bare ground under canopy of California-laurel than under canopy
of associated trees. Bioassay experiments showed that the leaf
and litter volatiles, leachates, and extracts of laurel are
capable of inhibiting germination and growth of several test
species (56,61).
The distribution of California-laurel in the Coast Ranges south of
San Francisco appears to represent a vegetational continuum (61).
About the same mixture of understory plants was found under
California-laurel canopies as under associated trees, but
California-laurel and some of its associates seemed to have a
greater tendency to spread to other communities than species from
those communities to invade California-laurel woodland.
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Rooting Habit
provided by Silvics of North America
The root system of California-laurel has
been described as fleshy, deep, and widespreading (49). Several
exceptions have been noted, however. Root wads of windthrown
trees from alluvial soil in southern Oregon were limited in
extent and without a prominent taproot (50). Root systems of
seedlings and young trees dug near Berkeley, CA, had relatively
shallow root systems, as did some fallen older trees (28). Over
half the roots in representative California-laurel stands in the
Berkeley Hills were distributed in the top 30 cm. (12 in) of Los
Osos adobe clay and all were in the top 90 cm. (36 in) (34). In
contrast to the paucity of information on the shape and extent of
the root system of California-laurel, its root structure has been
thoroughly investigated (26,27).
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Seed Production and Dissemination
provided by Silvics of North America
Seed crops are abundant
in most years. Although umbels bear four to nine flowers each,
generally only one to three fruits set (24). The age when a tree
first bears fruit, the age for maximum production, and the
average quantity produced have not been determined. Seeds are
produced in abundance after trees are 30 to 40 years old (20).
Drupes fall stemless to the ground in late autumn or winter and
are dispersed by gravity, wind, animals, and water (34). Fallen
drupes are easily gathered by hand. The drupes are large and
heavy; 454 g (1 lb) of drupes may yield about 300 cleaned seeds
(39).
Under favorable natural conditions, seeds on the ground retain
viability over winter, but, under adverse conditions, viability
may prove very transient. Viability has been maintained for 6
months when seeds were stored at 3° C (37° F) in wet,
fungicide-treated vermiculite (34).
Fresh, untreated seeds germinate indoors or outdoors in peat moss,
sawdust, vermiculite, or light-textured soil but may require 3
months or longer (25,39,60). Germination can be speeded by
scarifying, cracking, or removing the endocarp, or stratifying
the seed, but up to 2 months may still be required (25,34,60). In
comparison tests made in petri dishes, California-laurel
germination was highest in 30 days under a temperature regime of
16° C (61° F) day, 7° C (45° F) night, and
when evaporative stress was minimal (34). Germination did not
appear to be affected by light level but was highest in soil with
moisture tension at 4 to 10 atmospheres.
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Seedling Development
provided by Silvics of North America
Germination occurs naturally in
autumn soon after seedfall, or in late winter and spring (52).
Covered seeds germinate best, but the large seeds are not buried
readily without ground disturbance or silt deposition by high
water. Seedling establishment is not common in the drier parts of
California except in protected areas and where ground is
disturbed (24). California-laurel seedlings invade grasslands and
brushlands in the Berkeley Hills; similar capabilities were
observed in the Santa Cruz Mountains (34,61).
Germination is hypogeal, and the fleshy cotyledons remain within
the endocarp and attached to the seedling until midsummer, when
the plant may be 15 to 20 cm (6 to 8 in) tall (25,48). Generally
there are two large cotyledons, sometimes three, and no
endosperm. Seedlings produce leaves of several transitional forms
as they develop and do not branch until they are 2 or 3 years old
unless induced to do so by removal of the terminal bud. They soon
develop a moderately stout taproot and are difficult to
transplant if more than 1 year old unless grown in containers.
Recovery after transplanting is often slow, and height growth may
be limited for several seasons.
Young California-laurel seedlings appear flexible in their growth
requirements. In the first 120 days, seedlings potted in
vermiculite grew well at several levels of temperature,
evaporative stress, soil moisture, and soil nutrients (34).
Seedlings grown at 18 percent or more of full sunlight produced
the most dry weight.
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Special Uses
provided by Silvics of North America
Wood of California-laurel compares favorably in machining quality
with the best eastern hardwoods (8) and is used for fancy turned
woodenware, interior trim, cabinets, furniture, paneling, veneer,
and gunstocks. Burls and other growths with unusual grain are
especially prized for making gifts, novelties, and wood carvings,
all marketed as myrtlewood. The wood of mature trees is
moderately heavy, hard, fine grained, rich yellowish brown to
light gray, and often beautifully mottled. The wood of younger
trees generally has less distinctive grain and markings. By rough
estimate, 19 950 to 22 800 m³ (3.5 to 4 million fbm) are
used annually in the myrtlewood industry.
Indians and early settlers used all parts of the tree for food and
medicinal purposes (6,21). Leaves are still collected and dried
for home use and commercial sale as a food seasoning (5,37,61).
The leaves, seeds, and wood have strong chemical properties and
should be used for food, seasoning, or medicinal purposes with
caution (5,9,36,48,61).
California-laurel is used for hedges, windbreaks, and indoor and
outdoor ornamental evergreens (3,29,41,43). It also provides food
and cover for wildlife (53). Silver gray squirrels, dusky-footed
woodrats, California mice, and Steller's jays feed extensively on
the seeds (54,55). Hogs eat both seeds and roots. Young sprouts
are choice browse for deer and goats in spring and summer (33,47)
when volatile components of leaves are at lowest concentrations
(30).
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Vegetative Reproduction
provided by Silvics of North America
California-laurel can be
reproduced by cuttings (60), but techniques need further
development. Under natural conditions, it may sprout prolifically
from the root collar, stump, and trunk. Sprouts and suckers
develop wherever a canopy opening admits strong light from the
side or overhead. Stumps ringed with root-collar sprouts and both
fallen and standing live trunks entirely enveloped in new green
sucker growth are common (24). Crowns formed by clumps of sprouts
growing in the open typically assume a distinctive, very dense,
and symmetrically rounded shape (12,50).
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Distribution
provided by Silvics of North America
The range of California-laurel spans more than 11° of
latitude, from below the 44th parallel in the Umpqua River Valley
of Douglas County, OR, south beyond the 33d parallel in San Diego
County, CA. In the Coast Ranges, the southern limit is on eastern
slopes of the Laguna Mountains, a short distance from the Mexican
border (19). In the Sierra Nevada, it extends as far south as the
west slope of Breckenridge Mountain in Kern County (58). Eastward
from the coast, California-laurel extends to the foothills of the
Cascade Range in Oregon and California, into the western Sierra
Nevada for its entire length, and to the inland side of the Coast
Ranges south of San Luis Obispo, CA. Its farthest extent inland,
about 257 km (160 mi), is in the southern Sierra Nevada.
- license
- cc-by-nc
- copyright
- USDA, Forest Service
Brief Summary
provided by Silvics of North America
Lauraceae -- Laurel family
William L. Stein
California-laurel (Umbellularia californica) is the most
valued and best publicized hardwood species in the Western United
States. It is a monotypic, broadleaved evergreen with many common
names, including bay, laurel, California-bay, Oregon-myrtle,
myrtlewood, Pacific-myrtle, spice-tree, and pepperwood (50). The
names are derived from leaf, fruit, or wood characteristics and
also from some similarities often mistaken for relationships with
the myrtle and laurel trees of the Mediterranean area (12,25).
Decorative items made from the hard, beautifully grained wood are
widely marketed as myrtlewood.
- license
- cc-by-nc
- copyright
- USDA, Forest Service