BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Ceanothus cuneatus | Wedgeleaf Ceanothus 



GENERAL BOTANICAL CHARACTERISTICS : 
Wedgeleaf ceanothus is a rigid, warm-season, evergreen shrub which grows
from 3 to 12 feet (1 to 3.5 m) in height [43,61].  Plants frequently
form dense, impenetrable thickets [61,66].

Branches are thorny, rigid, and covered with a grayish pubescence [61].
The thick, leathery leaves are opposite, entire to thinly toothed at the
tip, and mostly obtuse [43,61].  Leaves are grayish-green and glabrous
above, and paler beneath [43].  The showy flowers occur in small, dense,
rounded umbellate clusters [43,48,55].  Flowers are generally white or,
less commonly, light blue to lilac [55,64], and have a sweet-scented,
"balsamlike" fragrance [64].  Shiny, black, round to oblong seeds are
borne in subglobose capsules [43].  Wedgeleaf ceanothus is noted for its
ability to fix atmospheric nitrogen [67].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Wedgeleaf ceanothus is most often described as a nonsprouter, or
obligate seeder [8,35,44,45,54].  Regeneration from exposed roots or
root crowns has also been reported, although it is probably extremely
rare and of minimal importance [14,66].

Seed:  Cleaned seed averages 49,000 to 54,000 per pound (108-119 g)
[52,66].  Hard-coated, shiny seed is contained in a subglobose capsule
which breaks apart explosively at maturity, dispersing seed away from
the parent plant [9,35,43,61].  Plants begin producing seed at
approximately 4 to 5 years of age [9].  Some seed is produced annually,
but the size of the seed crop varies [9].  Weather conditions during the
preceding year may significantly influence seed production.  Seed
predation by small mammals and insects may be severe.  Rodents have
reportedly removed up to 99 percent of the annual ceanothus seed crop in
some areas [13].

Seed dispersal:  Seed of wedgeleaf ceanothus can be cast up to 35 feet
(11 m) from the parent plant [9], but most seed falls beneath the
canopy.  Evans and others [17] reported that 32 percent of wedgeleaf
ceanothus seed was dropped beneath the canopy, with 42 percent located
at the edge of the plant.  The remaining seed was dispersed outward to
30 feet (11 m) from the parent plant.  Most seed was cast in a
southwesterly direction.

Seed dispersal is often completed in a relatively short period of time.
Approximately 95 percent of all seed was cast within 14 days in the
central Sierra Nevada of California [17].  A specific threshold of
temperature and moisture may be necessary to initiate seed casting [17].

Germination:  Wedgeleaf ceanothus germinates in large numbers after fire
[52,55,64].  Exposure to heat apparently stimulates seed germination by
increasing permeability to water [52].  Hot water soaks at 160 degrees
Fahrenheit (71 deg C) for 12 hours are effective in breaking seed
dormancy [11].  In laboratory tests, approximately 40 to 50 percent
germination was obtained under dry heating at temperatures of 194 to 212
degrees Fahrenhiet (90-100 deg C) [4].  Seeds planted 0.5 to 1 inch
(1.2-2.5 cm) deep show best emergence in either sun or shade [1,52].

Although seeds germinate best after fire, exposure to fire is not
essential for germination [8].  In some areas a few seedlings emerge in
openings in the absence of fire [9].  Seeds in openings are apparently
exposed to high enough temperatures through solar heating to cause
scarification and subsequent germination [4].  New seedlings rarely
emerge from beneath dense brush [9].

Seedbanking:  The seed of wedgeleaf ceanothus remains viable for long
periods of time [21,55,64].  Although the maximum length of viability
has not been documented, seed apparently remains viable for at least
several decades.  Approximately 98 percent of seed aged 17 years and 5
months germinated in carefully controlled laboratory experiments [50].
Large numbers of seed accumulate in the soil, litter, or duff beneath
parent plants during fire-free intervals [17,45].  This pool of buried
seed, partially insulated from the most extreme temperatures, germinates
after fire [4].

Seedling establishment:  Most natural seedling emergence occurs in March
or April, with emergence 80 percent complete by the middle of April [5].
Most seedlings emerge during the first year after fire, although a few
emerge during the second postfire year [62].  Seedling mortality is high
during the first few years [13,21] and often ranges from 36 to 68
percent by the third year after fire [25].  During the first few years
seedlings are vulnerable to drought, competition from other species, and
herbivory [9,25,55].


SITE CHARACTERISTICS : 
Wedgeleaf ceanothus commonly grows in semiarid valleys and interior
foothills on dry slopes, alluvial fans, and gravelly, open ridges
[14,43,55,61].  This shrub is a constituent of southern California
chaparral communities, but becomes dominant in central and northern
California chaparral [15].  Wedgeleaf ceanothus is an important
component of many drier conifer forests dominated by ponderosa (Pinus
ponderosa) or Jeffrey pine (P. jeffreyi) [14], and occurs in
pinyon-juniper and oak (Quercus spp.) woodlands [10,13,43].  This shrub
grows as a scattered understory species in some locations, but
frequently forms dense, pure stands [7,55].

Soils:  Wedgeleaf ceanothus typically grows on shallow, well-drained,
gravelly soils [13,48,55].  This shrub is also noted for its ability to
grow well on nutrient-poor serpentine soils of southern Oregon and
northern California [67].

Elevational range:  Wedgeleaf ceanothus generally grows from 300 to
4,000 feet (91-1,219 m) in elevation, although more rarely occurs up to
6,000 feet (1,829 m) [43,55].



SUCCESSIONAL STATUS : 
Facultative Seral Species

Wedgeleaf ceanothus is known for its wide ecological amplitude [44], and
can occur as either a seral or climax species [15].  In the Klamath and
Rogue regions of southern Oregon, it grows as a climax species, often
intermixed with oaks (Quercus spp.), on xeric slopes immediately above
the valley floors [2,15,33].  These harsh, arid sites are subject to
extreme diurnal and seasonal temperature variation [2].  In other, often
more mesic, portions of Oregon chaparral, wedgeleaf ceanothus is
successional to oaks (Quercus spp.) [15].

The successional status of wedgeleaf ceanothus in California chaparral
is less well-known.  Many consider chaparral dominated by wedgeleaf
ceanothus to represent fire-induced climax communities [41].  Hanes [29]
aptly notes that succession here is "more a gradual elimination of
individuals present from the outset than a replacement of initial shrubs
[such as wedgeleaf ceanothus] by new species."  Wedgeleaf ceanothus
frequently retains its importance in northern California chaparral
communities for a period of 100 years or more [33].  However, Noble and
Slatyer [45] report that once an established chaparral community in
southern California has matured, wedgeleaf ceanothus generally dies out
within 50 years.  Limited evidence suggests that this shrub is
relatively more important in later seral or even climax communities
towards the northern edge of its range.


SEASONAL DEVELOPMENT : 
In southern California chaparral wedgeleaf ceanothus undergoes most
active vegetative growth during late winter and spring [3].  The growth
of new leaves, initiation of flowerbuds, and branch elongation all occur
simultaneously [3].  Wedgeleaf ceanothus flowers from March through May
or June [14,43,52], and fruit ripens from April through June [52].  Seed
may be cast from June through August, with dispersal peaking in July
[3,17].  Although leaves of wedgeleaf ceanothus persist throughout the
year, many are lost during the summer [3].

Related categories for Species: Ceanothus cuneatus | Wedgeleaf Ceanothus