• GENERAL BOTANICAL CHARACTERISTICS
• RAUNKIAER LIFE FORM
• REGENERATION PROCESSES
• SITE CHARACTERISTICS
• SUCCESSIONAL STATUS
• SEASONAL DEVELOPMENT

GENERAL BOTANICAL CHARACTERISTICS:

Grouse whortleberry is a low, rhizomatous, usually matted, slow-growing native shrub that reaches 4 to 20 inches (10-51 cm) in height. Plants are multi-branched from the base and broomlike in appearance. The small, thin leaves are deciduous; flowers are urn-shaped and inconspicuous. Berries are 0.12 to 0.2 inch (3-5 mm) broad [43,58,97,129,140].

Most Vaccinium spp. lack a taproot but have fine, threadlike lateral roots [74]. Roots of grouse whortleberry grow to a depth of about 16 inches (40 cm). Rhizomes occur in duff, or at the interface of duff and mineral soil, and are restricted to the upper 4 inches (10 cm) of soil [40,87].

RAUNKIAER [101] LIFE FORM:

Chamaephyte
Geophyte

REGENERATION PROCESSES:

Grouse whortleberry reproduces through seed and vegetatively through rhizome sprouting. The edible berries contain many seeds that are probably dispersed by birds and mammals.

Vaccinium seeds are not dormant. Seedlings may emerge 1 month after dispersal and continue to emerge for long periods without cold temperatures. Seedlings of most western Vacciniums are apparently rare in the field. Seedling establishment may be important only on good sites during "favorable" years [26,109].

Grouse whortleberry sprouts from rhizomes growing in the forest floor [87]. Because they are relatively shallow, rhizomes are vulnerable to fires of high severity and mechanical treatments that include severe soil scarification [10,68].

SITE CHARACTERISTICS:

Grouse whortleberry is one of the most prominent understory species in the subalpine zone of the Rocky Mountains [1,82]. The species is common in coniferous forests, ravines, or on open slopes across a relatively wide geographical and elevational range [59,76,112,131].

Sites dominated by grouse whortleberry are characterized by heavy snowpack, although early season snowmelt is common. In many areas, the potential for drought exists by midsummer. These sites are usually cool to cold with a very short growing season [46,48,76].

Grouse whortleberry grows on dry to moist, well drained, rocky, sandy and gravelly loams [6,33,54,56,112]. Vaccinium spp. require acidic soils and thrive where pH ranges from 4.3 to 5.2. These shrubs require relatively low amounts of many essential elements and are capable of growing on soils with low fertility [74].

Grouse whortleberry has a wide elevational range [139]. Ranges reported in the literature are as follows:

6,000 to 7,200 feet (1800-2,200 m) in California [58]
8,500 to 12,500 feet (2,590-3,810 ) in Colorado [49]
4,800 to 9,000 feet (1,460-2,740 m) in Montana [96,99]
7,870 to 8,360 feet (2,400-2,550 m) in Wyoming [65]

SUCCESSIONAL STATUS:

Grouse whortleberry occurs as a seral or climax dominant in many high-elevation conifer forests [10,76,84,99,110]. In some high-elevation mountain hemlock or subalpine fir-lodgepole pine forests, grouse whortleberry declines as the overstory canopy closes [44,63].

In southwestern Montana, whitebark pine/grouse whortleberry overstories are relatively even-aged and can reach 400 to 600 years in age between stand-replacing disturbances. Nonlethal underburns occur more frequently than stand-replacing fires [13,91]; grouse whortleberry persists through low-severity fires. Please refer to the Fire Ecology and Fire Effects sections of this report for more information.

Following clearcutting that does not lead to heavy mechanical scarification in Rocky Mountain lodgepole pine stands, grouse whortleberry often sprouts and occupies a prominent role in seral communities. With moderately heavy site or slash treatments, grouse whortleberry decreases dramatically. High initial cover of species such as fireweed (Epilobium angustifolium) and pearly everlasting (Anaphalis margaritacea) often develops immediately after disturbance in many Rocky Mountain lodgepole pine-subalpine fir communities of western Montana. However, these understories succeed to grouse whortleberry and beargrass as the pole canopy develops [10]. Although lodgepole pine is often regarded as a seral species, some lodgepole pine/grouse whortleberry communities of the northern Rockies a represent an edaphic vegetation climax [34].

SEASONAL DEVELOPMENT:

Grouse whortleberry flowers in early to midsummer. Fruit maturation begins immediately after flowering, and fruit is generally ripe by late summer or fall [43,126].

Phenological development was documented as follows during a study in the northern Rockies [113]:

         East of the Continental Divide - MT and Yellowstone NP 

         leaf   leaves  flower  flower  fruit  seed   leaves 
         bud    full    starts  ends    ripe   fall   fallen
         burst  grown                          starts 

average  5/17   6/12    6/8     6/26    8/7   8/13   9/28 
earliest 4/30   5/21    5/1     5/10    7/22   8/3    9/12
latest   6/30   7/25    7/4     7/21    8/15   8/20   10/24

         Northern Idaho and western Montana -

         leaf  leaves  flower  flower  fruit  seed  leaves
         bud   full    starts  end     ripe   fall  fallen
         burst grown                          start       
                                                                  
average  5/3   5/26    5/17    6/2    7/21    8/14   10/4
earliest 3/27  4/25    4/15    5/15   7/5     8/10   9/5
latest   5/28  6/30    6/12    7/2    8/29    8/23   10/16

Related categories for SPECIES: Vaccinium scoparium | Grouse Whortleberry