Bilberry

Fire temperature:  The effect of temperature on the sprouting ability of
whortleberry in Scotland was documented as follows after 17 months of
regrowth [62]:

                        aboveground temperatures
                        (degrees C for 2 minutes)
                      
                        400          600           800

mean # sprouts/plant    180           51            22
mean % cover            133           68            16
mean height (cm)         22           17            14
mean biomass (g)         85           30             3

whortleberry
dwarf bilberry

More info for the term: cover

Whortleberry provides some cover for small birds and mammals.  The
diverse canopy layers associated with subalpine fir/whortleberry
forests of the Southwest reportedly serve as good habitat for deer, elk,
and many species of birds [32].  Cover value of whortleberry has been
rated as follows [26]:

                          UT     WY

Pronghorn                poor   poor
Elk                      poor   poor
Mule deer                poor   poor
Small mammals            good   good  
Small nongame birds      fair   good
Upland game birds        fair   fair

More info for the terms: adventitious, fruit, peat, shrub

Whortleberry is a slender-branched, somewhat spreading, dwarf
deciduous shrub which reaches 4 to 18 inches (10-18 cm) in height
[57,87,92,97,105].  Plants are typically shorter at higher elevations
[100].  This rhizomatous shrub generally forms open colonies [92].
Roots are fibrous and much branched, with maximum diameters of 0.06 to
0.08 inch (1.5-2.0 mm) [41].  Numerous fine adventitious roots form an
interconnected mat in the top 2 inches (5 cm) of peat [41].

Twigs are green or less commonly yellowish, glabrous or puberulent, and
sharply angled [43,50,92,97].  Stems often become reddish or
orange-tinged when exposed to full sunlight [87].  Branches tend to be
thicker and less numerous than the morphologically similar grouse
whortleberry [43], and whortleberry lacks the unique broomlike
branching typical of grouse whortleberry [87].  Whortleberry also has
larger leaves and flowers and often puberulent stems [98].  Stem
morphology has been examined in detail [69].  The maximum age of aerial
shoots is generally estimated at 15 years [92].  However, in parts of
Sweden, stem ages average 18 years [20].

Small, simple, alternate leaves are ovate to lanceolate or broadly
elliptic with serrate margins [50,92,98].  Leaves are acute to obtuse at
the apex and rounded to broadly cuneate at the base [97,98].  Leaves are
light green and 0.4 to 1.2 inches (1-3 cm) in length [43]. 
Whortleberry leaves turn red, yellow, or brown in autumn [95].

The pink, cream, or greenish-white flowers are borne singly in the axils
of new stems [73,92,98].  Flowers are small, waxy, and urceolate to
campanulate [43,50].  Fruit of whortleberry is a spherical berry 0.2
to 0.3 inch (5-8 mm) in diameter [43,65].  Fruit color ranges from dark
red to bluish or purplish black [43].  Whortleberry is single-fruited
[65].  Berries are generally not glaucous, although a glaucous bloom is
occasionally observed [73,92].  Berries contain many nutlets which
average approximately 0.04 inch (1 mm) in length [92,97].

Whortleberry grows from British Columbia southward east of the
Cascades to central Oregon [42,92].  It occurs throughout the Rocky
Mountains from British Columbia and Alberta to northern New Mexico and
southern Arizona [92,98].  Whortleberry reaches greatest abundance in
the southern Rockies, whereas the closely related and morphologically
similar grouse whortleberry is most abundant in the Northwest [13,20]
Disjunct populations of whortleberry have been reported in the
interior Rocky Mountains [92].  This circumboreal species extends across
Europe and Asia [42,92].  Populations in southwestern Greenland are
believed to have originated from European plants [92].

More info for the terms: fire regime, seed, shrub

Whortleberry appears well adapted to a regime of fairly frequent
fires.  In parts of Britain and presumably elsewhere, it commonly
persists on sites burned at "periodic" intervals [7,62].  However, this
shrub also thrives under longer fire intervals.  In parts of the central
and southern Rocky Mountains, it assumes dominance later than the first
century after fire [16].  Relatively long fire intervals have also been
reported in whortleberry forests of Sweden, where mean fire
frequencies are estimated at approximately 91 years [35].

Whortleberry is generally capable of sprouting from an extended
network of underground rhizomes after aboveground vegetation is
destroyed by fire.  Regeneration through seed is reportedly poor on
burned, previously forested sites [35].  Although some researchers
consider whortleberry to be a seed banker [29,35], seedlings are
apparently rare [81].  Some seed may be carried to burned sites by birds
and mammals [35,81].

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".

More info for the terms: cover, crown class, crown fire, duff, fire management, fire suppression, forest, frequency, fruit, fuel, fuel loading, fuel moisture, habitat type, litter, prescribed fire, scarification, severity, snag

Wildlife:  Evidence suggests that fire suppression may be having an
adverse impact on bear habitat in some areas [102,110].  Once-productive
berry fields are being invaded by conifers.  Since plants beneath a
forest canopy generally produce few berries, fruit production has been
steadily declining in many areas [65].  Berry fields can be treated with
fire if maintenance or enhancement of berry crops is a prime management
objective.  Logging treatments which include severe soil scarification
or slash burns may also reduce berry production.  Even where timber
harvest favors berry production, lack of cover in early years can limit
bear use.  Wildfires often create diverse habitat mosaics which
incorporate elements of hiding cover and favor bear use [102].

Prescribed fire:  Flower buds tend to be more numerous on new shoots,
and periodic removal of old shoots can increase flower production in
Vacciniums.  Prescribed fire has long been used to rejuvenate commercial
low sweet blueberry (V. angustifolium) fields and to increase overall
fruit production [64].  Prescribed fires, particularly those conducted
during the spring when soil moisture is high, may increase berry
production for wildlife species.  Little research has been conducted on
whortleberry, although the use of prescribed fire has been evaluated
with respect to blue and globe huckleberries [64,65].
 
Fuels:  A whortleberry understory partially supports fine fuels such
as needle litter and small twigs and produces a more optimally aerated
fuel bed.  Estimated fuel loading of whortleberry has been established
for lodgepole pine forests of the southern Rocky Mountains [2].

Timber harvest:  In spruce-fir forests of the southern Rocky Mountains
of New Mexico, forest regeneration after fire may be most rapid in cover
types dominated by Vacciniums such as whortleberry [27].


FIRE CASE STUDY
SPECIES: Vaccinium myrtillus
FIRE CASE STUDY CITATION :
Tirmenstein, D., compiler. 1990. Effects of a prescribed crown fire on
whortleberry on Table Mountain, Washington. In: Vaccinium myrtillus. In:
Fire Effects Information System, [Online]. U.S. Department of Agriculture,
Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory
(Producer). Available: https://www.fs.fed.us/database/feis/ [
var months = new Array(12);
months[0] = "January";
months[1] = "February";
months[2] = "March";
months[3] = "April";
months[4] = "May";
months[5] = "June";
months[6] = "July";
months[7] = "August";
months[8] = "September";
months[9] = "October";
months[10] = "November";
months[11] = "December";
var date = new Date();
var year = date.getFullYear();
var month = date.getMonth();
var day = date.getDate();
document.write(year+", "+months[month]+" "+day);
].


REFERENCE :
Woodard, Paul Michael. 1977. Effects of prescribed burning on two
different-aged high-elevation plant communities in eastern Washington.
Seattle, WA: University of Washington. 228 p. Dissertation. [111].


SEASON/SEVERITY CLASSIFICATION :
September 30, 1975  - severity not reported.


STUDY LOCATION :
The study site is located in Kittitas County, Washington on the east
side of the Cascades, approximately midway between Ellensburg and
Wenatchee.


PREFIRE VEGETATIVE COMMUNITY :
Two areas, both of which occur in the subalpine fir zone, were included
in the study.  Both sites were representative of the Engelmann spruce
(Picea engelmannii)-subalpine fir (Abies lasiocarpa)-elk sedge (Carex
geyerii) habitat type as delineated by Wirsing (1973).  The lodgepole
pine thicket site was described as a "well-developed,
well-differentiated" stand.  All layers of the overstory were well
stocked with lodgepole pine, the dominant overstory species.  Subalpine
fir and Engelmann spruce codominated the intermediate crown class.
Common understory dominants included elk sedge (Carex geyerii),
heartleaf arnica (Arnica cordifolia), broadleaf arnica (Arnica
latifolia), Hood sedge (Carex hoodii), bigleaf lupine (Lupinus
polyphyllus), and whortleberry (Vaccinium myrtillus).

The snag site consisted of decadent lodgepole.  Many snags were present
in the overstory with living lodgepole pine, subalpine fir, and
Engelmann spruce.  Subalpine fir and Engelmann spruce occurred as
overstory codominants although only subalpine fir was regenerating
beneath the closed canopy.  Subalpine fir, elk sedge, broadleaf arnica
(Arnica latifolia), pinegrass (Calamagrostis rubescens), and the mosses
Rhacomitrium canescens var. ericoides and Polytrichum commune were
common understory dominants.

Subplots at both sites were thinned to 20 percent of the original crown
cover prior to the burn.


TARGET SPECIES PHENOLOGICAL STATE :
not reported


SITE DESCRIPTION :
        elevation - 5,600 to 5,800 feet (1,706-1,761 m)
        slope - 0 to 20 percent
        aspect - south to west, primarily southwest
        topography - much relief
        soils -
                parent material - basalt residuum
                bedrock composition - basalt, andesite, rhyolite
                soil fertility -
                        lodgepole pine thicket - low
                snag - moderate
        climate -
                winters - cold and wet
                summers - cool and dry
                annual precipitation - 31.5 to 63 inches (80-160 cm)
                70 percent of annual precipitation occurs as snow
                between October and March


FIRE DESCRIPTION :
        time of fire - 1400 to 1600 hours
        ambient air temperature - 61 to 63 degrees F (16-17 degrees C)
        relative humidity - 19 to 21 percent
        wind direction - south to southwest, erratic
        wind speed - calm, gusts to 16 miles per hour (26 km/hour)
        days since rain - 15
        fuel moisture (fine) - 13.1 percent
        estimated flame heights - 125 to 140 feet (38-42 m)
        fire description - A back fire was ignited on the north side
                with 9 foot (3 m) strips, then a strip head fire was
                applied to the remainder of area at 49 foot intervals.
                Hand-held drip torches containing a 50/50
                diesel oil-gasoline mixture were used to ignite the
                fire.
        mean duff reductions -
                        lodgepole pine thicket - from 60 tonnes/ha to
                                4 tonnes/ha
                        snag - from 74 tonnes/ha to 49 tonnes/ha
 



FIRE EFFECTS ON TARGET SPECIES :
Comparative frequency and cover of whortleberry were documented as
follows:

Lodgepole pine thicket -

                rel. frequency                    rel. cover
        before tmt.   1 yr. after         before tmt.     1 yr. after

burned      .46           .38                 .013            .012
control     .75          1.00                 .078            .070
thinned     .20           .20                 .019            .002

Snag -

                rel. frequency                    rel. cover
        before tmt.   1 yr. after         before tmt.     1 yr. after

burned       .12          .06                  .001           .000
control      .25          .50                  .009           .004
thinned      .20          .20                  .001           .013

Whortleberry regenerated from rhizomes after fire, but in general,
postfire response was poor.


FIRE MANAGEMENT IMPLICATIONS :
Crown fires can kill or drastically reduce sprouters such as whortleberry.

Crown fires can kill or drastically reduce sprouters such as whortleberry.

More info on this topic.

More info for the terms: geophyte, phanerophyte

   Phanerophyte
   Geophyte

Whortleberry grows in open woods, on hillsides, high ridges, hummocky
seepage slopes, and moraines [4,49,92].  In mountains of the Southwest,
it occurs on all slopes and aspects at higher elevations [32]. 

Climate:  Upland spruce-fir sites occupied by whortleberry are often
cold and steep [47].  On many sites, snow commonly persists until late
spring [32].

Soils:  Most Vacciniums require acidic soils and can grow on infertile
sites which have relatively small amounts of many essential elements
[53].  Whortleberry requires little potassium and can grow well where
ammonium is the only source of nitrogen [46].  In Scandinavia,
whortleberry appears to be most abundant on sites of intermediate fertility
[20].  It is commonly associated with raw humus in parts of northeastern
Scotland and Scandinavia [107,108].  It commonly grows on shallow, rocky
soils in the southwestern United States [101].  Growth is generally
marginal on poorly aerated soil [53].

Elevation:  Whortleberry typically grows at middle to high elevations.
Elevational range by geographic location is as follows
[26,49,100,85,92,98]:

      from 7,000 to 12,000 feet (2,134-3,660 m ) in the Southwest
           8,000 to 11,000 feet (2,438-3,355 m) in AZ
           7,500 to 13,000 feet (2,286-3,965 m) in CO
           4,300 to 8,000 feet (1,311-2,438 m) in MT
           9,500 to 11,000 feet (2,896-3,965 m) in UT
           8,500 to 8,500 feet (2,591-2,591 m) in WY
           656 to 3,800 feet (200-1,150 m) in Britain
           > 5,250 feet (1,600 m) in the Cascades and Rocky Mtns.       
           3,000 to 5,000 feet (914-1,524 m) east of the Cascades

More info on this topic.

This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

   205  Mountain hemlock
   206  Engelmann spruce - subalpine fir
   210  Interior Douglas-fir
   211  White fir
   217  Aspen
   218  Lodgepole pine
   219  Limber pine
   227  Western redcedar - western hemlock
   237  Interior ponderosa pine

More info on this topic.

This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

   FRES20  Douglas-fir
   FRES21  Ponderosa pine
   FRES23  Fir - spruce
   FRES24  Hemlock - Sitka spruce
   FRES26  Lodgepole pine
   FRES28  Western hardwoods

More info on this topic.

This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the term: forest

   K002  Cedar - hemlock - Douglas-fir forest
   K004  Fir - hemlock
   K011  Western ponderosa pine
   K012  Douglas-fir forest
   K013  Cedar - hemlock - pine forest
   K015  Western spruce - fir forest
   K018  Pine - Douglas-fir forest
   K019  Arizona pine forest
   K020  Spruce - fir - Douglas-fir forest
   K021  Southwestern spruce - fir forest

Portions of stem bases occasionally survive light fires.  Underground
regenerative structures of whortleberry generally survive all but
extremely hot fires [90].  Rhizomes, which occur at depths of 0.24 to
1.2 inches (6-30 mm) [41,90], can survive fires in which soil surface
temperatures reach 820 degrees F (438 degrees C) [90].  However,
rhizomes are sometimes destroyed on severely burned sites [90].

Seeds of most Vacciniums are of short viability and are readily killed
by heat [64].

More info for the terms: fruit, tree

Browse:  A variety of small mammals consume the twigs, leaves, and bark
of whortleberry [57,71].  Throughout most of Scandinavia,
whortleberry is the primary winter food of the gray-sided vole
(Clethrionomys rufocanus) [57].  Browse appears to be of negligible
value to large ungulates.

Fruit:  Berries of whortleberry are eaten by many birds and mammals
[56] including the ring-necked pheasant, hares, grouse, partridges,
ptarmigans, and bears [35,74,81].  In Finland, these berries make up a
high percentage of brown bear diets during August.  Coniferous forests
with a whortleberry understory provide essential brown bear habitat
during late summer in parts of Scandinavia [74].  Whortleberry was
presumably of similar importance to grizzly bears in North America prior
to their extirpation from the central and southern Rocky Mountains.
Vaccinium berries are readily eaten by the band-tailed pigeon, wild
turkey, gray catbird, ruffed, spruce, blue, and sharp-tailed grouse,
tanagers, bluebirds, thrushes, quails, and towhees [63,92,94].  The
white-footed mouse, gray fox, red fox, raccoon, pika, deer mouse, and
numerous species of chipmunks, ground squirrels, tree squirrels, and
skunks also feed on Vaccinium fruit [54,63,94].

More info for the terms: association, climax, codominant, forest, habitat type, mesic, natural, series, woodland

Whortleberry is a common understory dominant or codominant in a
variety of coniferous forests of the Rocky Mountains.  It occurs in
abundance in stands made up of subalpine fir (Abies lasiocarpa),
Douglas-fir (Pseudotsuga menziesii), Engelmann spruce (Picea
engelmannii), and white fir (Abies concolor).  Whortleberry is also an
understory dominant in lodgepole pine (Pinus contorta), ponderosa pine
(P> ponderosa), western hemlock-western redcedar (Tsuga
heterophylla-Thuja plicata, and quaking aspen (Populus tremuloides)
communities.  Common understory codominants include grouse whortleberry,
skunkleaf polemonium (Polemonium pulcherrimum), northern twinflower
(Linnaea borealis), and thimbleberry (Rubus parviflorus) [6,4,78,98].

Published classifications listing whortleberry as an indicator or
dominant in habitat types, community types, or plant associations are
presented below.

Classification of the forest vegetation of Wyoming [3]
Classification of the forest vegetation of Colorado by habitat type and
  community type [4]
Classification of the forest vegetation on the National Forests of
  Arizona and New Mexico [5]
A preliminary classification of the natural vegetation of Colorado [8]
Climax forest series of northern New Mexico and southern Colorado [23]
Forest habitat types south of the Mongolian Rim, Arizona and New Mexico [24]
Forest habitat types in the Apache, Gila, and part of the Cibola
  National Forests, Arizona and New Mexico [32]
Plant association of Region Two: Potential plant communities of
  Wyoming, South Dakota, Nebraska, Colorado, and Kansas [47]
Forest vegetation of the Gunnison and parts of the Uncompahgre National
  Forests: a preliminary habitat type classification [52]
Forest and woodland habitat types (plant associations) of northern New
  Mexico and northern Arizona [59]
The lodgepole pine zone in Colorado [66]
A forest habitat type classification of southern Arizona and its
  relationship to forests of the Sierra Madre Occidental of Mexico [68]
Forested plant associations of the Okanogan National Forest [99]

Plant associates:  Common associates of whortleberry include
thimbleberry, northern twinflower, kinnikinnick (Arctostaphylos
uva-ursi), mountain snowberry (Symphoricarpos oreophilus), heartleaf
arnica (Arnica cordifolia), common juniper (Juniperus communis), black
twinberry (Lonicera involucrata), Rocky mountain maple (Acer glabrum),
serviceberry (Amelanchier alnifolia), and grouse whortleberry
[8,25,47,52,68].  Where whortleberry and grouse whortleberry occur
together, whortleberry typically occupies somewhat lower, more mesic
sites [106].

More info for the term: shrub

Shrub

More info for the terms: cover, fruit, rhizome, scarification, tree

Berry production:  Berry production in whortleberry fluctuates
annually with weather conditions [31,56].  Spring frosts and summer
droughts can greatly decrease yields [31].  Production is typically good
in favorable, moist years, but during bad years no fruit is produced
over extensive areas [50].  Generally, fruit production is poor when
winter snow cover is less than 8 inches (20 cm) deep.  Buds are
vulnerable to damage by cold winter temperatures.  In some areas, flower
bud development may be greatly reduced when January temperatures have
reached -26 to -29 degrees F (-32 to -34 degrees C) [75].

The age of plant, canopy cover, stand age, and other site
characteristics can also influence berry production [56].  In some
areas, berry production may peak at stand ages of 20 to 70 years [20].
However, Kuchko [56] reports that in Finland, whortleberry can bear
fruit for "some time after clearcutting," suggesting optimal fruit
production occurs during somewhat earlier seral stages.  Very young
shoots often allocate more resources to vegetative growth than to fruit
production [71].  As branches age, growth often declines [71].

Livestock:  Livestock trampling can compact the soil and reduce rhizome
sprouting and vegetative expansion of whortleberry clones [7].  Stems
tend to be shorter where livestock numbers are high [95].

Chemical control:  Bilberries (Vaccinium spp.) exhibit variable
susceptibility to herbicides such as 2,4-D, 2,4,5-T, glyphosate,
karbutilate, and picloram [12,104].

Timber harvest:  Most species of Vaccinium are susceptible to
postlogging treatments which include heavy scarification [64].  This
appears to be true of whortleberry as well.  However, other types of
timber treatments may produce increases in cover.  In central Colorado,
whortleberry increased at all levels of tree thinning but declined
immediately after clearcutting [19].  Combined cover of whortleberry
and grouse whortleberry was as follows after various types of timber
harvest [18,19]:

                                    percent cover
                 before logging     years after logging
                                    1     2     3     4     5

control          32.4             34.0  36.4  31.0  30.7  35.7
clearcutting     17.2             12.6  18.3  18.8  14.7  22.4

                                    percent cover
basal area      before thinning     years after thinning
(ft sq/acre)                        1     2     3     4      5

control         15.9              15.5  16.9   17.9  16.5   17.0
120             18.8              11.5  17.5   21.4  23.1   26.2
 80             12.6               5.3   7.4   10.6  10.5   16.7
 40             14.4               3.3   5.9    7.9   9.6   10.5


Damage:  Large clones may be broken up by frost, fire, or burrowing
mammals [38].  In the absence of a protective layer of snow, plants are
vulnerable to cold winter temperatures and may be killed by exposure to
temperatures of 3 degrees F (-19.5 degrees C) [38].

Silviculture:  Whortleberry frequently serves as a nurse crop for
Douglas-fir seedlings [78].

Wildlife considerations:  Vaccinium berries are an extremely important
food source for bears.  In many areas, bear-human conflicts are most
likely to occur during years of berry (Vaccinium spp.) crop failure
[64,83].  Both black and grizzly bears typically exploit areas with
dense concentrations of berries.  The value of Vaccinium shrubfields as
grizzly bear habitat can be increased by permanent or at least seasonal
road closures, by coordinating timber harvest dates to have minimal
impact on habitat use patterns, and by considering the cumulative
effects of habitat modification across a broad area.  In general, site
preparation should include minimizing soil compaction, using cooler
broadcast burns rather than hot burns, or by eliminating site
preparation entirely wherever possible.  Grizzly use is favored where
hiding cover is retained by treating small, irregular patches instead of
large contiguous areas, and by leaving stringers of timber within larger
cuts [102].

More info for the term: forest

Browse:  Blueberry (Vaccinium spp.) foliage is relatively high in
carotene, manganese, and energy content [20,39,93].  Nutrient value of
whortleberry browse varies according to weather conditions, site
characteristics such as soil type and elevation, plant part, and timber
treatment [18,57,86,100].  Nitrogen content depends in large part on
available soil nutrients, with total leaf nitrogen typically increasing
with elevation [57,100].  Selected nutrient value of whortleberry
browse by timber treatment is as follows [18,86]:

                       subalpine forest - central Colorado -
                                  (percent)         

                                3 yrs                 5 yrs
                       uncut    clearcut         uncut       clearcut

crude protein          9.3        11.2            11.0         12.6
moisture              57.3        60.3            60.2         60.4
in vitro digest.      28.0        29.2            31.1         38.3

                        northwestern Montana -
                         (micrograms per g)

                  Ca    Cu   Fe    K    Mg    Mn    N    Na    P    Zn
clearcut - burn
         stem    6105   7.4   66  3895  1259 1059  6718  134  1232  53
         leaves  8950   9.7  113  9480  3061 1410 19040  160  2296  25
control - unburned
         stem    5100    --   92  2880   752 1200  9100  119   943  39
         leaves  8540  12.1  153  7460  1808 2770 25470 1721  1937  21

Fruit:  Vaccinium berries are sweet and contain high concentrations of
both mono- and disaccharides [88].  Berries are rich in vitamin C and
energy content but low in fats [45,77].

     AZ  CA  CO  ID  MT  NM  OR  UT  WA  WY
     AB  BC

More info for the terms: fresh, fruit

Fruit of whortleberry is juicy, edible, and has a "nutlike flavor"
[50].  Berries are eaten fresh or gathered for use in jams and jellies
[31,92].  Fruit may be used in pie filling [92]; however, collecting
enough of the small berries can be difficult [50].  Leaves of
whortleberry have been used to make tea [50].  Both fruit and leaves are
reported to have some medicinal value [56].  Vaccinium berries were
traditionally an important food source for many native peoples.  Fruit
of the whortleberry was traditionally used by the Kootenai, Carriers,
and Shuswap in North America, and by many indigenous peoples throughout
northern Europe and Siberia [92].

Whortleberry may have potential value for breeding commercial
fruit-producing strains [60], particularly those suited to upland
mineral soil [53].  Whortleberry may also be useful in developing
cold-hardy cultivars for northern plantings [21].  It is tolerant of
cold winter temperatures, and some strains may be hardy to -70 degrees F
(-57 degrees C) [21].

More info for the term: fruit

Whortleberry browse is described as "worthless" for cattle but on
occasion is of fair palatability to domestic sheep [22].  Palatability
to big game species appears slight.  Fruit of whortleberry is highly
palatable to a wide variety of birds and mammals.  Overall palatability
of whortleberry has been rated as follows [26]:

                      CO     UT     WY

Cattle               poor   poor   ----
Sheep                fair   fair   ----
Horses               poor   poor   ----
Pronghorn            ----   poor   poor
Elk                  ----   good   fair
Mule deer            ----   good   good
White-tailed deer    ----   ----   good
Small mammals        good   good   good
Small nongame birds  good   good   good
Upland game birds    ----   good   good
Waterfowl            ----   poor   poor

More info on this topic.

More info for the terms: formation, seed

Phenological development of whortleberry varies with climate,
latitude, and longitude [95].  New leafy shoots generally develop in
March or April [81].  In a Finnish study, annual vegetative growth began
as buds began to swell on May 13 [95].  By June 1, leaf buds had
completely opened and vegetative growth continued until early to
mid-June.  Leaves were colored or shed by October 19 [95].  The active
growth period lasted approximately 5 months.  Development tends to be
delayed at higher elevations [81].

Seed set and berry formation begins two to four weeks after pollination
[81].  Berry ripening is completed about 50 days after flowering [95].
Phenological development was documented as follows in a Finnish study
[95]:

                               average # of days (since Jan. 1)

  beginning of veg. dev.                   136.3
  leaf buds begin to open                  147.6
  leaf buds completely open                152.3
  start of budding                         150.6
  opening of flowers                       153.4
  cessation of growth                      176.3
  beginning of green berry phase           170.8
  berries ripening                         202.1
  autumn color begins                      222.6
  autumn color ends                        292.2

Generalized seasonal development by geographic location is as follows
[49,73,95,97]:

     location         flowering         fruiting
 
     n ID             May-August           --
     AZ               June-July            --
     Southwest        May                 July
     s Finland        mid-May              --
     n Finland        early June           --

More info for the terms: competition, cover, fire intensity, seed, severity, shrub

Vegetative response:  Whortleberry commonly sprouts from underground
rhizomes or, when damage is less severe, from axillary buds located at
the stem base [62,90].  Sprouting ability appears closely related to
fire intensity and severity [62].  Whortleberry generally sprouts
following all but hot fires [90].  A Colorado study suggests that
although postfire canopy cover is typically high on lightly burned
sites, this shrub may be virtually eliminated on severely burned areas
[109].  Postfire response is generally best in protected microsites or
on lightly burned areas [78,90].

Clonal vigor is often enhanced by fire.  Old, large, decadent clones are
often broken up by fire [38].  Surviving portions serve as isolated
centers of regeneration which give rise to the development of vigorous
daughter clones [81]. 

Seed:  Seedlings are rarely observed on burned sites [90].  Although
some researchers consider whortleberry to be a seed banker, adequate
documentation is lacking [See Regeneration].  Birds and mammals may
carry some seed to burned sites.

Postfire response:  Vegetative expansion of whortleberry may be rapid
after fire, particularly where competition is light [81].  Sprouting may
be evident within a few months after fires in which surface soil
temperatures reached as high as 820 degrees F (438 degrees C).  In
forests of northern Sweden, preburn cover can be reached within a few
years.  However, where underground rhizomes are destroyed by fire,
recovery may take a "very long time" [90].  On burned and clearcut old
growth forests of west-central Montana, whortleberry had not attained
preburned biomass within 10 to 14 years after disturbance [78].

More info for the terms: rhizome, root crown, shrub

   Small shrub, adventitious-bud root crown
   Rhizomatous shrub, rhizome in soil
   Initial-offsite colonizer (off-site, initial community)

More info for the terms: forest, fresh, fruit, rhizome, seed

Whortleberry can reproduce from seed or by vegetative means.

Vegetative regeneration:  Forms of vegetative regeneration appear to be
of primary importance after fire [81] or other disturbance.  However,
colonies increase laterally through rhizome expansion even in the
absence of disturbance.  Annual radial increases average 2.8 inches (7
cm) [(2 to 4 inches) (5-10 cm)] per year [81,92].

Whortleberry possesses an extensive, frequently branched network of
rhizomes averaging 0.12 to 0.24 inch (3-6 mm) in diameter [41].  The
total length of rhizomes occasionally exceeds 3.3 feet (1 m), but the
amount producing sprouts typically measures only 28 to 35 inches (70-90
cm) in length [7].  Rhizome depth ranges from 0.24 to 1.2 inches (6-30
mm) below the soil surface [41,90].  Sprouting ability declines with age
[7].  Although rhizomes of 23 to 28 years of age have been reported
[92], few rhizomes older than 15 years produce aerial shoots with new
growth [7].  The extensive rhizome network allows for rapid regeneration
after disturbance [81].  Where portions of the stem base survive,
regeneration through surviving aboveground axillary buds also occurs
[62].

Seed:  Whortleberry fruit contains an average of 18 to 20 viable seeds
per berry with an average of 18 imperfectly-formed seeds [81,91].  Seeds
weigh an average of 25 mg per 100 seeds [91].  Seed production generally
begins at age three [71] and is subject to considerable annual
variation.  [see Management Considerations - Berry Production].  Bees
are the primary pollinators [79].

Germination:  Germination averages 35 to 46 percent following various
types of pretreatment.  Germination of seed exposed to low temperatures
(32 degrees F [0 degrees C]) for 3 weeks averaged 41 to 64 percent [81].
Good germination has been reported after seeds were exposed to 14 hours
of light at 82 degrees F (28 degrees C) followed by 10 hours of darkness
at 55 degrees F (13 degrees C) [91].  Fresh seed germinated well under a
similar regime, or when exposed to alternating periods at 71 degrees F
(22 degrees C) and 41 degrees F (5 degrees C) [91].  Heat treatments
were found to produce some germination although the amount was irregular
[62].  The effect of temperature on germination was as follows [62]:

               effect of heat treatment on seed germination
               total germination after 24 weeks - percent -

              50 C            75 C             100 C

control        0               -                 -
30 sec        14               8                20
1 min          0               2                 6
2 min         16               0                 2

                effect of pretreatment on imbibed seeds after
                21 weeks at 0 degrees C -

 treatment                      percent germination

control                                64
cold only                               6
cold + 50 C for 1 minute               10
cold + 50 C for 2 minutes              14
cold + 50 C for 3 minutes              16
cold + 100 C for 1 minute               8
cold + 100 C for 2 minutes              4
cold + 100 C for 3 minutes              2

Seed banking:  Evidence for seed banking in whortleberry appears
contradictory.  Some researchers have observed very few seeds in the
soil despite high coverage at the site and doubt if seed banking is an
important regenerative strategy in this species [89].  Most Vacciniums
are characterized by seed of relatively short viability which is readily
damaged by heat [64].  However, others emphasize the importance of seed
banking in whortleberry [29,35,92].  Soil samples in Wales, for
example, have yielded 28 buried viable seeds per square foot (300 per/sq
m) [92].  In a Swedish forest, seeds were found in the lower humus layer
of 120-year-old stands as well as in the moss-litter layer of 50- and
169-year-old stands, suggesting a "continuous input of seeds" [35].
Seedlings were produced as follows from 25 buried soil cores, each of
which was 4 inches (100 mm) in diameter [35]:

   stand age     cover     frequency      seedlings produced
   (years)        (%)         (%)                (#)

       16          5           80                 22
       29         35          100                 10
       50         58          100                 93
      120         56          100                 49
      169         60          100                 95

In Sweden, single buried berries occasionally produced clusters of up to
20 seedlings [35].  Longevity of whortleberry seed has not been
documented, although Granstrom [35] reports that many buried seeds may
be "quite old."

Seed dispersal:  Seeds of whortleberry are widely dispersed by many
birds and mammals [35,81].  In laboratory tests, seedlings have
germinated from pellets of various lagomorphs [35].

Seedling establishment:  In many locations, including parts of northern
Europe, seedlings are rarely observed [81,90].  Seedlings of Vacciniums
are also rare in North America [92, (P. Stickney, pers. comm. 1990)].
However, seedling establishment of whortleberry appears variable.
Establishment is reportedly poor on burned sites, on scarified
clearcuts, and in mature closed canopy forests [35].  However, Vander
Kloet [92] reports that on favorable sites in Sweden, seedlings may
number 25 per square foot (270 per square meter).  Initial development
of seedlings is very slow [81].

More info on this topic.

This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

    5  Columbia Plateau
    6  Upper Basin and Range
    8  Northern Rocky Mountains
    9  Middle Rocky Mountains
   10  Wyoming Basin
   11  Southern Rocky Mountains
   12  Colorado Plateau

More info for the term: severity

September 30, 1975  - severity not reported.

More info for the term: snag

        elevation - 5,600 to 5,800 feet (1,706-1,761 m)
        slope - 0 to 20 percent
        aspect - south to west, primarily southwest
        topography - much relief
        soils -
                parent material - basalt residuum
                bedrock composition - basalt, andesite, rhyolite
                soil fertility -
                        lodgepole pine thicket - low
                snag - moderate
        climate -
                winters - cold and wet
                summers - cool and dry
                annual precipitation - 31.5 to 63 inches (80-160 cm)
                70 percent of annual precipitation occurs as snow
                between October and March

More info on this topic.

More info for the terms: climax, density, frequency, natural, shrub, succession

Whortleberry occurs as a climax dominant in many high elevation
spruce-fir forests of western North America [5,25,84].  In high
elevation Engelmann spruce-subalpine fir and lodgepole pine forests of
Colorado, it assumes prominence after the first postfire century,
following the decline of rose (Rosa spp.), grouse whortleberry, and
kinnikinnick.  During later stages, it commonly assumes dominance with
cliffbush (Jamesia americana) and common juniper (Juniperus communis).
Occurrence of whortleberry by stand age has been documented as follows
in Colorado [16]:

                         spruce - fir
                         stand age (years)

                   1   2   8    8   18   74   200    280   290   300   400
density (avg. #
    stems/plot)   -    -  66.6  45.0 -  171.0 151.5  79.2  96.3 132.8  136.8
frequency (%)     -    -  80    40      100   100    60    70   100     80

                          lodgepole pine
                          stand age (years)

                  8     18   18    85  108   115  190  248   251  257
density (avg. #
     stems/plot) 68.4  66.6  10.8 43.2 100.5  -   66.6 21.6  38.8 97.8
frequency (%)    40    80    20   80   100    -   80   21.6  60   100

In southern Finland, whortleberry becomes abundant during secondary
succession after species such as fireweed (Epilobium angustifolium) have
flourished and declined [96].

In some locations, this shrub may become important in early seral
communities.  In parts of Britain, whortleberry and mountain cranberry
commonly codominate heather communities soon after fire but then decline
in later successional stages [81].  Natural dieback of 12-year-old
bilberry stands has been reported [7].

Vaccinium oreophilum

More info for the terms: fruit, natural

The scientific name of whortleberry is Vaccinium myrtillus L. [48].
It is placed within section Myrtillus of the family Ericaceae [69,92].

The Vaccinium genus is taxonomically complex [14]. Hybridization and
polyploidy make delineation of species difficult [14,15]. Whortleberry
may have received genetic material from thinleaf huckleberry (V.
membranaceum) and dwarf bilberry (V. caespitosum) [13]. Naturally occurring
whortleberry-mountain cranberry (V. vitis-idaea) hybrids have been
reported in parts of northern Europe [1,37,60,79]. Numerous intermediate
forms have been observed, although fruit set is apparently rare in
these populations [44]. V. x intermedium Ruthe is a natural hybrid
resulting from a whortleberry-mountain cranberry cross [44,79,81].

More info for the terms: hardwood, rhizome, seed

The extensive rhizome network of whortleberry can aid in preventing
soil erosion once plants become established [93].  Species within the
genus Vaccinium can be propagated from hardwood stem cuttings or from
seed [17].  Root cuttings of whortleberry can be successfully
transplanted onto disturbed sites and mature plants can be transplanted
during the spring [9,33].  Vegetative propagation of whortleberry has
been examined in detail [92].  Vaccinium seedlings grown in the
greenhouse can be transplanted onto favorable sites 6 to 7 weeks after
emergence.  Seed collection and storage techniques have been well
documented [17].