BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Rubus ursinus | Trailing Blackberry 



GENERAL BOTANICAL CHARACTERISTICS : 
Trailing blackberry is a low-growing, trailing or climbing, native
evergreen shrub [9,27,55].  This mound-building shrub can grow to 15 or
20 feet (5-6 m) in length [6,13,55].  The densely prickled stems are
greenish when young but turn brown at maturity [9].  The somewhat
prickly, deeply-lobed, alternate leaves are palmate and a lighter green
color beneath [9,13,27].

The stems of most blackberries are biennial.  Sterile first-year stems,
known as primocanes, develop from buds at or below the ground surface
and produce only leaves.  Lateral branches, or floricanes, develop in
the axils of the primocanes during the second year and bear both leaves
and flowers [24].

Perfect flowers of trailing blackberry develop in clusters of 2 to 15
near the ends of leafy branches [9,13,55].  Fruit is red and hard when
immature but shiny black when ripe [6].  Fruit is oblong or conical,
somewhat bristly, and up to 0.8 inches (2 cm) in length [9,55].
Aggregates of druplets, commonly referred to as "berries," are sweet and
flavorful at maturity [9,27].


RAUNKIAER LIFE FORM : 
   Hemicryptophyte


REGENERATION PROCESSES : 
Trailing blackberry exhibits vigorous vegetative regeneration but also
commonly reproduces through seed.  Reproductive versatility is common in
the Rubus genus, with sexual reproduction, parthenogenesis (development
of the egg without fertilization), pseudogamy (a form of apomixis in
which pollination is required), and parthenocarpy (production of fruits
without fertilization) occurring widely.  The following types of
reproduction have been documented in blackberries:  (1) sexual
reproduction, (2) nonreduction at meiosis on the female, male, or both
sides, (3) apomixis (seed contains embryo of maternal rather than sexual
origin) with segregation, (4) apomixis without segregation, and (5)
haploid parthenogenesis [11].  These modes of asexual reproduction
contribute to the aggressive, vigorous spread of blackberries.

Vegetative regeneration:  Most species within the Rubus genus are
capable of vigorous sprouting from root or stem suckers, or rooting stem
tips [24].  Trailing blackberry sprouts readily from "suckers"
(presumably root suckers), or "nonrhizomatous sprouts" after fire or
mechanical disturbance [9,52,61].  It is also capable of spreading
rapidly from trailing stems which root at the nodes [37,65].  These
modes of vegetative spread occur even in the absence of disturbance.

Seed production:  Most blackberries produce good seed crops nearly every
year [6].  During the first year of development, blackberries grow from
perennial rootstocks or creeping stems and produce sterile vegetative
shoots known as primocanes [24].  Lateral branches which produce both
leaves and flowers (floricanes) develop in the axils during the second
year [24].  Black shiny drupelets are produced on the floricanes of
trailing blackberry [6].  Fruit is oblong to conical, and up to 0.8
inches (2 cm) in length [55].  384,000 per pound (845,814/kg) [6].

Germination:  Blackberry seeds have a hard, impermeable coat and dormant
embryo; consequently, germination is often slow.  Most blackberries
require, as a minimum, warm stratification at 86 to 68 degrees F (30 to
20 degrees C) for 90 days, followed by cold stratification at 36 to 41
degrees F (2 to 5 degrees C) for an additional 90 days [6].  These
conditions are frequently encountered naturally as seeds mature in
summer and remain in the soil throughout the cold winter months.
Laboratory tests indicate that exposure to sulfuric acid solutions or
sodium hyperchlorite prior to cold stratification can enhance
germination [3].

Seed dispersal:  Fruit of the trailing blackberry is readily dispersed
by many small birds and mammals [27].  After they mature, the sweet,
succulent berries rarely remain on the plant for long [6].

Seedbanking:  The seeds of most blackberries remain viable for at least
several years after being buried in the soil or duff [6].  Although the
precise length of viability has not been determined for the trailing
blackberry, Morgan and Neuenschwander [52] regard it as a species which
relies heavily on seedbanking for postfire regeneration.  Average seed
densities of 290 per foot square (27 per m sq) have been reported in
western redcedar (Thuja plicata)/pachistima and western redcedar/
queencup beadlily (Clintonia uniflora) habitat types in coniferous
forests of northern Idaho [55].


SITE CHARACTERISTICS : 
The trailing blackberry occurs across a wide range of sites from warm,
open areas to dense woodlands [27,36].  It is particularly common in
prairies, clearings, waste places, and canyons [36,55].  Trailing
blackberry frequently assumes prominence on sites which have been burned
or logged [16,27,36] and on river terraces or gravel bars dominated by
red alder (Alnus rubra) [19].

Soils:  Blackberries (Rubus spp.) grow well on a variety of barren,
infertile soils [6].  These shrubs tolerate a wide range of soil texture
and pH but require adequate soil moisture for good growth [10].
Trailing blackberry appears to be tolerant of periodic flooding by
brackish or fresh water [65].

Elevation:  Trailing blackberry grows from sea level along the Pacific
Coast to middle elevations farther inland [27,36].  Generalized
elevational ranges for given locations are as follows [9,13]:

        < 2,000 feet (610 m) in the Santa Monica Mtns., CA
        < 3,000 feet (914 m) in southern California


SUCCESSIONAL STATUS : 
Trailing blackberry is a vigorous competitor which commonly invades
disturbed sites created by logging, fire, or other types of disturbance
[16,39].  It is particularly well represented following "catastrophic
disturbance" in Douglas-fir forests of the Pacific Northwest [25], and
readily established on mudflows and other harsh microsites following the
eruption of Mount St. Helens.  Trailing blackberry typically increases
rapidly on disturbed sites, persisting until suppressed by canopy
closure [26].  It occurs in stands of all ages but reaches greatest
abundance in early seral communities [16,37,44].  Although primarily an
early seral species, trailing blackberry can sometimes persist in low
densities as a residual species in mature forest communities [16,59].
Trailing blackberry was observed in initial postdisturbance, early
immature, late immature, mature, and old growth stands in coniferous
forests of southwestern British Columbia [44].  This shrub increases
rapidly and can dominate the herbaceous layer as early as 2 to 5 years
after disturbance [25].  In many western hemlock-western redcedar or
Douglas-fir forests of the Pacific Northwest, this shrub remains
dominant for at least 20 years after disturbance [2,25].  Bailey [2]
found that trailing blackberry increased to 50 percent cover 4 years
after disturbance, fluctuated between 25 and 50 percent cover for 20
years, and declined to 1 percent cover in climax stands.  Maximum cover
values were reached 15 to 30 years after logging and fire in Douglas-fir
plantations in western hemlock-Douglas-fir habitats of western Oregon
[59].
 
Trailing blackberry is present in red alder communities, which on
certain upland sites, appear to represent early seral stages of western
hemlock forests.  Where these communities occur along streambanks,
periodic flooding can maintain species such as salmonberry and red alder
in long-lived, disclimax situations.  Trailing blackberry is considered
a major dominant in early successional stages of these communities [33].


SEASONAL DEVELOPMENT : 
Seasonal development of the trailing blackberry varies according to
geographic and climatic factors.  Phenology has been documented as
follows [6,9,13,27]:

     location         flowering     fruit ripening     seed dispersal

        --            April-June    June-August        July-September
        --            April-Aug.         --                  --
Santa Monica Mts.,CA  Feb.-June          --                  --
      s CA            March-July         --                  --

Trailing blackberry remains dormant during the winter [12].

Related categories for Species: Rubus ursinus | Trailing Blackberry