BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Rubus laciniatus | Evergreen Blackberry 



GENERAL BOTANICAL CHARACTERISTICS : 
Evergreen blackberry is a semierect to erect and arching, much-branched
shrub which grows up to 10 feet (3 m) in height [30,33].  These shrubs
often grow in a dense cluster [32].  Stems often trail at the ends and
are covered with numerous stout, curved thorns [32,33].

The stems of blackberries are generally 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 [14].

Evergreen leaves have five leaflets and are palmately or, less commonly,
pinnately compound [33].  Leaves are green on both surfaces, but hairy
beneath.  Leaflets are lacinate to dissected [18].

Perfect white-to-pink or rose flowers are borne in compound paniculate
cymes [32,33].  Fruit of the evergreen blackberry is large, round, and
shiny black in color [30,32].  Fruit grows up to 0.8 inch (2 cm) in
length and is made up of a few large, sweet, succulent drupelets
[4,30,32].


RAUNKIAER LIFE FORM : 
   Hemicryptophyte


REGENERATION PROCESSES : 
Evergreen blackberry regenerates both sexually and through vegetative
means.  Reproductive versatility is well represented 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 fruit 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
with segregation, (4) apomixis without segregation, and (5) haploid
parthenogenesis [7].  These modes of asexual reproduction help
contribute to the vigorous, aggressive spread of blackberries.

Vegetative regeneration:  The mostly biennial stems of blackberries
typically develop from perennial rootstocks or creeping stems located
aboveground.  Most species within the Rubus genus are capable of
vigorous sprouting from root or stem suckers and rooting stem tips [14].
Evergreen blackberry produces numerous adventitious root suckers, even
in the absence of disturbance [15].  These root suckers are presumably
capable of producing new primocanes as the connection to the parent
plant is eliminated.  Evergreen blackberry also spreads rapidly as
aboveground vegetation roots at the nodes [20].  Evergreen blackberry
typically sprouts vigorously following disturbance.

Seed:  Most blackberries produce good seed crops nearly every year [4].
During the first year of development, blackberries grow from perennial
rootstocks or creeping stems and produce sterile vegetative shoots known
as primocanes.  Lateral branches (floricanes) develop in the axils
during the second year which produce both leaves and flowers [14].
Immature fruit of the evergreen blackberry is a dull red [4].  Ripe
berries are shiny black, and made up of relatively few large drupelets
[4,31,32]. Cleaned evergreen blackberry seed averages approximately
137,000 per pound (301,762/kg) [4].  Apomixis is particularly common in
the evergreen blackberry [15].

Germination:  Blackberry seeds have a hard impermeable coat and dormant
embryo [2,14]; consequently, germination is often slow.  Most
blackberries require, as a minimum, warm stratification at 68 to 86
degrees F (20 to 30 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 [2].  These conditions are frequently encountered
naturally, as seeds mature in summer and remain in the soil throughout
the cold winter months.  Scarification also appears to improve
germination.  Laboratory tests indicate that exposure to sulfuric acid
solutions or sodium hyperchlorite prior to cold stratification can
enhance germination [2].  Evidence suggests that avian digestive
processes can also help scarify the seed of blackberries [14].  Results
of specific germination tests of blackberry seed are as follows [14]:

 seed      pregerm.           last germ.     real amount     potential
 fed to:   treatment          of seed        of germ.        germ. (%)
           (in days)          (in # of       (%)          (% seeds still
                               days)                       alive at end
                                                           of test) 
                                        
waxwing    none                 --                0               50
waxwing    warm 90 + cold 90    --                0               51
Am. robin  none                 --                0               66
Am. robin  warm 90 + cold 90    41               17               60
n. catbird none                 --                0               59
n. catbird warm 90 + cold 90    49               21               72
control    none                 --                0               81
control    warm 90 + cold 90    27                3               81
        
Researchers observed that although some seed was mechanically damaged
while being ingested, intact seeds typically exhibited improved
germination [14].  These test findings emphasized the importance of
prior cold stratification for best blackberry germination.

Seedbanking:  Blackberry seed is typically long-lived when buried in the
soil or duff [2,15].  Researchers have located viable buried seed of the
evergreen blackberry at depths of 0 to 2 inches (0-5 cm) in coastal
Douglas-fir (Pseudotsuga menziesii) forests of British Columbia [12].

Seed dispersal:  Seed of evergreen blackberry is primarily animal
dispersed [1].  After they mature, the highly sought-after fruits rarely
remain on the plants for long [2].


SITE CHARACTERISTICS : 
Evergreen blackberry grows in a wide range of sites throughout much of
North America.  It is most commonly naturalized on waste ground or
disturbed areas [1033].  Evergreen blackberry has escaped from
cultivated gardens in many areas [4].

Soils:  Blackberries grow well on a variety of barren, infertile soils
[4].  These shrubs tolerate a wide range of soil texture and pH but
require adequate soil moisture for good growth [6].

Elevation:  Evergreen blackberry grows from sea level along the Pacific
Coast to higher elevations farther inland.  Evergreen blackberry has
been reported at 5,600 feet (1,707 m) in Colorado [8].


SUCCESSIONAL STATUS : 
Evergreen blackberry is primarily regarded as an early seral species.
It has been reported on initially disturbed and early immature stands in
coniferous forests of southwestern British Columbia [25].  Evergreen
blackberry is also abundant in old field communities and on disturbed
sites in the Northeast.


SEASONAL DEVELOPMENT : 
Seasonal development of the evergreen blackberry varies according to
geographic location and climatic factors.  Specific phenological
development has been documented as follows [4,30,33]:

     location       flowering     fruit ripening     seed dispersal

     California     May-July            --                  --
     Carolinas      May-June      June-July                 --      
     Northeast      June-August   July-October       September-October
     Pacific Coast  June-August   August-September   October-November

Related categories for Species: Rubus laciniatus | Evergreen Blackberry