BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Cornus canadensis | Bunchberry 



GENERAL BOTANICAL CHARACTERISTICS : 
Bunchberry is a low, rhizomatous subshrub with erect, mostly herbaceous
stems 2 to 8 inches (5-20 cm) tall [49,96].  There is a terminal whorl
of four to seven true leaves.  The small white flowers are borne in
clusters above four white or pinkish bracts which makes the entire
inflorescence resemble a single flower [55].  The coral-red fruits look
like berries but are actually drupes [49,96].

Bunchberry has a clonal habit which allows it to maintain itself under a
canopy.  In Alaska, clones are often roughly circular, but rhizomes
ramble across the forest floor and over or through decaying logs [90].
The rhizomes have annual increments of wood [18].  The longest living
rhizome found in one study was 172 inches (436 cm), and its age was
estimated at 36 years exclusive of early growth, which was already dead
[90].  In British Columbia, bunchberry rhizomes generally grow between 2
and 5 inches (5-13 cm) below the surface of the mineral soil [60].
However, another British Columbia study found bunchberry rhizomes in the
organic layer [69,70,71,21,73].  In Alaska, the "thread-like" rhizomes
were found 1 to 3 inches (2-8 cm) below the forest floor [90].  In New
Brunswick bunchberry rhizomes were found in mineral soil at a mean depth
of 3.1 inches (8 cm) with a range of 1.6 to 5.1 inches (4-13 cm) [24].

Tappeiner and Alaback [90] describe bunchberries growing in old growth
forests with canopy openings, young stands with dense canopies, and open
clearcuts:

                 Old stand          Young stand       Clear-cut
                 mean    range      mean    range     mean    range

Size of clone    64 in   (30-172)   6 in    (1-14)    122 in  (87-274)
(rhizome length) 165 cm  (77-436)   15 cm   (3-35)    309 cm  (220-696)

Height           3.5 in  (3-6)      1.6 in  (0.4-4)   4 in    (2-5)
                 9 cm    (8-14)     4 cm    (1-10)    10 cm   (5-12)

Annual growth
of rhizomes      4.7 in  (0-12)     1.2 in  (0.4-2)   24 in   (7-45)
                 9 cm    (3-22)     3 cm    (1-5)     131 cm  (42-230)

Nodes/clone      9       (3-22)     1       (1-3)     62      (18-114)

Nodes/m of 
rhizome          6       (3-11)     -----             20      (16-27)


RAUNKIAER LIFE FORM : 
   Chamaephyte
   Geophyte


REGENERATION PROCESSES : 
Bunchberry appears to be self-sterile and is dependent on pollinators
such as bumblebees, solitary bees, beeflies, and syrphid flies [7,18].
The flowers have one petal with an awnlike extension that initiates the
explosive release of pollen [18].  Results of one study show low (21.5%)
fruit-set after controlled cross-pollination, and significantly lower
(10.7%) fruit-set after open pollination.  In the same study, other
factors also affected reproductive success.  Buds did not open, fruit
development did not occur, and developing fruit aborted, suggesting that
fruit-set is resource limited.  Possible limiting factors include low
light levels and nutrient-poor soils [7].  Seeds of bunchberry are
dispersed by birds and mammals [62].  The seeds of bunchberry are much
smaller than those of other dogwoods, which may be an adaptation to seed
dispersal by mice and/or mouse predation [89].

Bunchberry seeds have dormant embryos and need cold stratification.
Details of treatment are given in Brinkman [9].  Normally seed of
bunchberry germinates over a 3-year period, with most of the seed
germinating in either the first or second year.  Further study of
bunchberry germination found good (61-87%) germination in the laboratory
and good germination (72-85%) in packets placed on the soil surface, but
germination was poor (1-8%) in fine mesh packets placed 0.4 inches (1
cm) under the forest floor.  Seed placed beneath the forest floor that
did not germinate within 1 year, did germinate in the laboratory.  Low
light levels may have caused the low germination rates, although other
factors such as low temperature were not ruled out [90].

A light requirement for germination could be useful to a species that
stores seed in the soil.  Soil-stored seed of bunchberry has been found
in Alberta [31], in Minnesota [4], in Maine [68], and in Quebec [62].  A
postfire test of buried seed germination in a northern Saskatchewan
white spruce, jack pine (Pinus banksiana), aspen (Populus tremuloides),
and balsam poplar (P. balsamifera) forest found bunchberry seedlings
comprised 5.2 percent of the total sample [6].

Early growth and clonal development are slow and survival is low (13
percent by the fourth year).  After 3 years, seedlings averaged 1 inch
(25 mm) in height, and by 4 years no rhizomes had been produced [90].

The establishment of new bunchberry plants from seed is low due to low
fruit set [46], low germination and survival rates, and slow early
growth.  Although some new seedlings are established, bunchberry is a
clonal perennial that relies heavily on vegetative regeneration to
maintain itself and spread.  It responds vigorously to disturbance [90].
By September 1980 following the May 18 eruption of Mount St. Helens,
bunchberry had sprouted from rhizomes in previously clearcut areas,
blowdown, and scorched sites [61].  It was growing on ripped up tree
roots where pieces of rhizomes had survived [39].


SITE CHARACTERISTICS : 
Bunchberry prefers moist, well-drained sites [26].  It is considered a
facultative wetland plant, which is sometimes found in wetlands but is
usually found on uplands [76].  It is considered to be indicative of
very moist sites [51] and of moist soils with moderately good drainage
[79].  In southeastern Alaska where bunchberry's range overlaps with
that of Lapland cornel, bunchberry is consistently a forest species,
while Lapland cornel is found in bogs.  Hybrids between them are found
on intermediate sites [66].  In Wisconsin, bunchberry is primarily a
boreal forest plant, although it is frequent in open bogs and occurs in
dry forest types as well [13].  It is also found on high levees and can
tolerate poorly drained forest sites [5].  The limitations on
bunchberry's range to the south may be due to its preference for cool,
acidic soils and its inability to survive in soils warmer than 65
degrees F (18 degrees C) in the summer [99].

Soils:  In northern Idaho, bunchberry grows more abundantly on soils
relatively low in organic matter (2-5.5%) and on granitic rather than
quartzite soils [64].  It prefers a pH of 7.0 to 7.9, although it grows
on soils with pH from 3.0 to 7.9 [51].  A perhaps more common view of
bunchberry is that it is an "acid loving" species [14].  In peatlands of
the boreal forest it is classified as very eutrophic, although it grows
on a wide range of sites [51].  In rich swamp forest it is an indicator
of minerotrophic water with pH 5.8-7.0, calcium 10-25 p/m, and calcium +
magnesium 13-30 p/m [45].

Elevation:  Elevational ranges in some western states are as
follows [15]:

                            Minimum              Maximum
                         feet     meters      feet     meters
Colorado                5,700     1,737      11,000     3,353
Montana                 3,200       975       6,600     2,012
Wyoming                 4,600     1,402       9,000     2,743


SUCCESSIONAL STATUS : 
In Alaskan Sitka spruce-western hemlock forests, bunchberry had 11.3
percent cover under gaps and only 0.87 percent cover under the forest
canopy.  In comparison with other understory species it is more shade
tolerant than salmonberry (Rubus spectabilis) and less shade tolerant
than fernleaf goldthread (Coptis asplenifolia), Alaska blueberry
(Vaccinium alaskaense), and red huckleberry (Vaccinium parvifolium) [5].
A shade frame study in Manitoba found little difference in frequency of
bunchberry growing in different shade frames, but cover increased
extremely rapidly in plots with 0 percent shade and more rapidly in
plots with 25 percent shade than those with 50 to 100 percent shade
[50].

During secondary succession on disturbed Sitka spruce-western hemlock
forest sites in Alaska, bunchberry may become a dominant species on
moist microsites within the first 3 years.  It then continues to be a
dominant understory plant until around 40 years when the pole-sized,
overstory canopy becomes dense and continuous.  As the overstory
matures, the canopy opens and becomes stratified.  At around 150 years,
bunchberry biomass may increase sharply and continue to rise as the
old-growth stage is reached [5].

On Alaskan white spruce sites, bunchberry is a common species by the
mixed hardwood-spruce stage (55-90 years).  By this time tree stands
have thinned out sufficiently to allow light to reach the understory
[16].  Another report on Alaskan white spruce shows bunchberry
increasing to a peak in the tall shrub-sapling stage (3-30 years),
decreasing as trees become dense (26-45 years), then increasing in the
hardwood stage (45-150 years), and remaining constant or decreasing
slightly into the spruce stage (150-300 years).  The pattern on Alaskan
black spruce (Picea mariana) sites is very similar, although
bunchberry's cover reaches a peak in the mixed hardwood-spruce stage
(55-90 years) [25].  A study of Michigan red maple (Acer rubrum)-eastern
white pine forests initially dominated by bigtooth aspen (Populus
grandidentata), found bunchberry had its greatest frequency at 50 years
[81].  In northwestern Montana red cedar (Thuja plicata)-western hemlock
forests, bunchberry frequency is higher early in succession and
decreases sharply in the climax forest [36,37].


SEASONAL DEVELOPMENT : 
Phenology for bunchberry in various areas is as follows
[15,46,62,65,82]:

                 Flowering           Fruit Ripening     Fruit Dispersal

California       May-July
Colorado         June-July           August
Montana          June-July           August
North Dakota     June-July           August
New Brunswick    June-early July     mid July-August    Aug.-October 
New England      mid May-July        
 2nd flowering   mid Aug.-Sept.
Newfoundland     June-July           late August        late Aug.-Oct.  
Quebec           May-July            Late July-Oct.
Wyoming          June                August

Related categories for Species: Cornus canadensis | Bunchberry