BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Vaccinium myrtilloides | Velvetleaf Blueberry 



GENERAL BOTANICAL CHARACTERISTICS : 
Velvetleaf blueberry is a dwarf, deciduous shrub which grows from 4 to
35 inches (10-89 cm) in height [10,78,86,90].  This rhizomatous shrub
commonly forms small open colonies [88].  However, on favorable sites, a
single plant may reach 33 feet (10 m) in diameter [90].  Velvetleaf
blueberry typically develops an extensive network of roots and woody
rhizomes [76,90].  The numerous shallow roots are fibrous and
much-branched, with considerable lateral spread [5,77].  Roots average
0.004 to 0.02 inch (0.1-0.5 mm) in diameter [5].  Taproots may be absent
[77], although at some sites, taproots averaging 0.4 inch (10 mm) in
diameter have been reported at depths to 3 feet (91 cm) [29,53].
Elsewhere, researchers have observed maximum rooting depths of 4 to 6
inches (10-15 cm) [84].  Clonal variation in the number of shoots and
rhizomes, and in rhizome depth has been reported [77].

Branches are velvety pilose [76] and ascending [90].  Twigs are green or
brown [88] and the bark, a "dirty brown" or green [90].  Stem morphology
has been examined in detail [60].  The thin, alternate, entire leaves
are elliptic to sublanceolate and 0.8 to 1.6 inches (2-4 cm) in length
[10,78,90].  The leaf base is obtuse or cuneate and the apex acute
[78,86].  The upper leaf surface is bright green whereas the
undersurface is paler [86].  Leaves are variable [86] but, as the name
velvetleaf blueberry suggests, are usually pubescent on both sides [88].

White to greenish, pale pink or purple-tinged flowers [10,78,86] are
borne in terminal or lateral racemes [90].  Flowers are drooping,
urceolate, or broadly cylindric-campanulate in shape [68,86,90].  Floral
morphology has been examined in detail [65].  Velvetleaf blueberry is
cluster-fruited species [19].  Fruit is a bright, frosty blue to dark
blue, or, less commonly, white (as in the form chicococcum) berry which
averages 0.16 to 0.4 inch (4-10 mm) in diameter [78,86].  Berries are
generally glaucous [88] and contain several small seeds or nutlets 0.04
inch (1.0 mm) in length [88,90].  Berries contain an average of 16
viable seeds; 100 seeds weigh approximately 26 mg [90].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Velvetleaf blueberry is capable of reproducing vegetatively or by seed.
However, regeneration after fire and other types of disturbance is
primarily vegetative [28].

Vegetative regeneration:  Velvetleaf blueberry is characterized by an
extensive network of woody rhizomes.  Rhizomes are generally
much-branched laterally, and give rise to many fibrous roots and shoots
[77,90].  Rhizomes usually grow rapidly in several directions once
plants reach 8 to 12 inches (20-30 cm) in diameter [90].  Depth, length,
and annual radial growth rates appear to be highly variable [77].
Rhizomes average approximately 0.15 inch (4 mm) in diameter and extend 3
to 46 feet (1-14 m) in length [29,77].  Rhizomes typically occur from
1.8 to 3.5 inches (4.5-9.0 cm) below the soil surface [53], although
depth depends on genetic factors and on site characteristics such as the
thickness of organic soil.  Normal rhizome depth is apparently inversely
related to the thickness of organic soil.  In eastern Canada, mean depth
of underground regenerative tissue in velvetleaf blueberry is 3.1 inches
(8 cm) [23,24].  In Alberta, shoots may occasionally develop from
rhizomes as deep as 4.3 inches (11 cm) [77].  Approximately 73 percent
of all shoots developed terminally on rhizomes, with 27.7 percent
developing from the middle [77].  Smith [77] reported rhizome length and
depth as follows in an Alberta study:

                                  sites
                           1      2       3      4       5      6 

average length (cm)      143.7  325.7   422.3  625.8   735.5  653.1    
average depth (cm)         6.8    8.5    7.1    6.9     4.5    9.0  
avg. # of sprouts/100 cm
   of rhizome length       1.2    1.5    2.2    1.9     1.6    1.0
organic horizon            3      6      7      7      10      3 
   thickness (cm)
slope (degrees)           40     10      3      2       3     20 
aspect                    NE      S     NE      E      NE      S
tree cover (%)          81-100  41-60  81-100  81-100 21-40  0-20
# trees > 1 in.           27     12     32      28      5      4     

Velvetleaf blueberry also sprouts from the bole, stump, or stem base
when disturbances such as fire destroy only portions of the aboveground
foliage [5,11,88].

Seed:  Velvetleaf blueberry begins fruiting during the third growing
season [90].  It is generally considered to be self-sterile and requires
insect pollination for fruit set [1,58,90].  Bees are the most common
insect pollinators, with bumblebees the most effective [58,68].  Seeds
of velvetleaf blueberry can germinate on mineral or organic soils when
moisture and aeration are adequate [90].  

Germination:  Germination of velvetleaf blueberry has been described as
sporadic [87].  Germination rates have ranged from 20 to 30 percent in
carefully controlled laboratory experiments.  Seeds typically germinate
from 18 to 82 days after planting; germination tends to be bimodal with
large numbers of seeds germinating early and late [90].  Seeds of most
blueberries (Vaccinium spp.) are not dormant and require no pretreatment
for germination [15].  Radicles first develop approximately 20 days
after seeds are sown, cotyledons emerge within 31 days, and the first
leaves unfold in 48 days [90].

Seed dispersal:  Seeds of velvetleaf blueberry are readily dispersed by
various birds and mammals [58].  Evidence suggests that long-distance
seed dispersal by many birds and mammals can effectively increase
genetic diversity in the velvetleaf blueberry.  The American robin is a
particularly effective dispersal agent.  Fruit typically ripens just as
birds are preparing for seasonal migrations [90].  Vander Kloet and Hall
[90] report that viability is reduced by 10 percent after seed passes
through the digestive tracts of birds and mammals.  However, Krefting
and Roe [48] suggest that digestive processes may actually enhance
germination.  Seeds obtained from black bear scats apparently germinate
more readily than do those from uneaten fruit [71].  Composite samples
of velvetleaf and low sweet blueberry (50:50) were as follows [71]:
                               percent germination

                     uneaten fruit        seed from feces
unrefrigerated             9                    15
refrigerated              16                    20
 
Seedling establishment:  Initial growth is typically slow wherever
significant competition is present such as in oldfield communities [90].
Plants may require 5 years to reach 6 inches (15 cm) in diameter [.


SITE CHARACTERISTICS : 
Velvetleaf blueberry is common in drier, relatively infertile conifer
types [90].  Velvetleaf blueberry also grows in forested portions of
bogs, in muskegs, peatlands, treeless mountain slopes, alpine meadows,
mountain meadows, barrens, headlands, boreal forests, and on rock
outcrops [10,68,88].  It commonly reaches greatest abundance on
disturbed sites such as in clearcuts or on recent burns [88,90].

Light regimes:  Evidence suggests that conditions necessary for the
growth of velvetleaf blueberry differ in eastern and western North
America.  On foggy, low elevation sites in New Brunswick, shade appears
to have a detrimental effect on the growth and development of velvetleaf
blueberry [77].  However, on dry, intensely sunny sites in Alberta,
shade enhances growth by aiding in water conservation [77].  Velvetleaf
blueberry is generally tolerant of shade and grows well in open woods
[30,33].  Hoefs and Shay [37] note that it prefers low light intensity
although some researchers report that berry production is enhanced in
sunny locations [86].

Climate:  Velvetleaf blueberry grows across a wide range of climatic
conditions [90].  It grows in perhumid climates on the East Coast and in
dry subhumid or cool, temperate climates in the West [43,90].  In the
West, its abundance increases with greater continentality [43].  Growing
season length ranges from 60 to 200 days [53,90].

Soils:  Most blueberries (Vaccinium spp.) require acidic soils and can
grow on infertile sites which have relatively small amounts of many
essential elements [44].  Velvetleaf blueberry grows on a wide variety
of soil types including well-drained coarse, or light-textured soils.
It occurs on fine sandy soils, loam, clay loam, till, and lacustrine
deposits [14,39,53].  Velvetleaf blueberry generally reaches greatest
abundance on moderate to light, often sandy, well-drained soils with
adequate soil moisture [77,90].  Soils are generally acidic, with pH
ranging from 3.0 to 5.9 [34,40].  Soils are commonly nitrogen-poor
[43,50] but may be rich in organic matter [34,43].  Organic content
ranges from 3 to 93 percent [90].

Elevation:  Velvetleaf blueberry grows from sea level to 3,950 feet
(0-1,200 m) [90].  Generalized range by geographic location is as
follows [20,86]:

                       from 3,200 to 4,300 feet (975-1,311 m) in MT
                       > 2,950 feet (900 m) in VA


SUCCESSIONAL STATUS : 
Velvetleaf blueberry commonly reaches greatest abundance in young
postdisturbance communities [90].  In the East, velvetleaf blueberry
vigorously colonizes disturbed sites such as clearcuts, recently burned
pine forests, and oldfields [78,88,90].  Throughout New England and the
Maritime Provinces, it colonized old farms which were abandoned in the
early part of the twentieth century [88].  Velvetleaf blueberry often
forms dense stands during seral stages after clearcutting in balsam
fir-red spruce forests [90].

Residual velvetleaf blueberry plants commonly colonize burned sites in
northern boreal forests [78] and elsewhere.  Reestablishment is often
rapid, particularly after light to moderate fires [see Plant Response to
Fire].  Velvetleaf blueberry can assume prominence within 2 to 3 years
after fire in jack pine woodlands [83].  In parts of parts of British
Columbia, velvetleaf blueberry commonly assumes dominance soon after
fire on dry to intermediately moist sites but is typically absent from
wet sites [36].  After hot fires in northern Ontario, velvetleaf
blueberry was initially replaced by more fire-tolerant species such as
Fremont sedge (Carex aenea), poverty oatgrass (Danthonia spicata), and
sweet fern (Comptonia peregrina) [71].  An extended period of moss and
grass dominance may occur prior to velvetleaf blueberry reestabishment
on severely burned sites [78].  In parts of eastern Canada, a
wintergreen (Gaultheria procumbens)-Canada beadruby-velvetleaf
blueberry-bunchberry association commonly develops under a regime of
frequent, light fires.  However, a bunchberry-velvetleaf
blueberry-kalmia-bracken fern association is more typical where fire
intervals are longer and fires more severe [23].  In northern Quebec,
low sweet blueberry may gradually replace velvetleaf blueberry on burned
areas as velvetleaf blueberry becomes restricted to shady sites [53].

Velvetleaf blueberry can persist in a variety of mature or climax forest
stands.  Limited evidence suggests that it is more tolerant of shade
than other sympatric species of Vacciniums.  It can survive in closed
stands, including white spruce-balsam fir forests, but flowering is
generally limited to forest openings [90].  Flowering and fruiting is
typically much reduced or absent in dense shade in all community types
[99].



SEASONAL DEVELOPMENT : 
Phenological development of velvetleaf blueberry varies according to
weather conditions, geographic location, and the genetic complement of
the individual clone [5,90].  In eastern Ontario, vegetative buds begin
to swell in late April or early May, as night time temperature exceeds
42 degrees F (6 degrees C) for 4 or 5 days at a time.  Leaves harden by
mid-June and turn red in early October or as early as July or August in
drought years [90].  Leaves generally absciss by late October.
Elongation of vegetative shoots ceases in June [5], and plants
overwinter without leaves.  Phenological development in northeastern
Ontario has been documented as follows [78]:

 phenological stage                          mean # of days          
 
-   budbreak in spring                               23
-   # of days from loss of bud scales and
    swelling of flowerbuds until 50% of
    flowers open                                     28
-   # of days between vegetative budbreak
    and death of apical meristem                     28
-   # of days between vegetative budbreak
    and maturation of lateral buds                   60

Flowering occurs the spring, either before or during shoot development.
Flower primordia form in late summer after annual vegetative growth is
complete [5,90].  Flower buds begin to swell in late April or May [90].
Berries generally ripen 49 to 68 days after flowering [90].  Ripening
time is greatly influenced by precipitation, temperature, and various
site characteristics.  Annual variation in ripening is documented in the
following Ontario study [26]:

                          percent ripe
1979      August 22            80
          August 30           100
          September 5       overripe

                          percent ripe
1980      August 6             60
          August 20, 25       100
          September 2, 15     100
          September 22      overripe

                                     percent ripe
1981      August 12            20           20         --
          August 17-19         40           40         45
          August 24-25         50           50         60
          September 1-2        70           70         85
          September 9-10       90           85        100
          September 14-15     100          100         --
     
Generalized seasonal development by geographic location is as follows
[5,74,78,86]:

  location              flowering            fruiting

New England             May 15-June 22         ----               
c NY                    mid May                ----
e ON                    mid to late May        ----
ME, NB, NS, ne PQ, LB
n ON, n MB, SK, nAB, NT late May to early June ----
  BC                    late May to late June  ----
  VA                    May-June               July-August
s ME                    ----                   late June
  ON                    ----                   July-September

Related categories for Species: Vaccinium myrtilloides | Velvetleaf Blueberry