BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Mahonia repens | Oregon-Grape 



GENERAL BOTANICAL CHARACTERISTICS : 
Oregon-grape is a native, evergreen, perennial shrub with a low or
prostrate growth form [46].  Stem heights of 4 to 12 inches (10 to 30
cm) are common [63,72].  Each stem arises from a rhizome [46,63,72].
Roots have been observed extending to 6 feet (1.8 m) without being
concentrated at any depth, suggesting a long taproot that would make it
adaptable to a wide variety of sites [47].  The leaves are pinnately
compound and spine-tipped, and the berries are born in grapelike
clusters [72].


RAUNKIAER LIFE FORM : 
   Chamaephyte


REGENERATION PROCESSES : 
Sexual:  Oregon-grape flowers are cross-pollinated by bees, but those
not receiving pollen from another source are selfed.  Selfing frequently
does not result in fruit production [46], but good fruit crops are borne
almost annually from cross-pollinated plants.  Wildlife consume the
berries and may aid in seed dispersal.  Seed can remain viable for up to
5 years in sealed containers stored in unheated sheds [49].

Vegetative:  Vegetative growth is initiated from horizontally growing
rhizomes, found 0.5 to 2 inches (1.2-5 cm) below the mineral soil
[46,49,62].


SITE CHARACTERISTICS : 
Oregon-grape grows on thinly wooded slopes or shaded hillsides in rocky,
slightly moist soil, or occasionally on open hillsides [63].  It is
among the most resistant plants to leaf burn from exposure to the winter
sun [73].

Soils:  Oregon-grape is found on sandy loams to silts, sedimentary
shales and sandstones, and granitic soils in coniferous forests
[46,63,72].  In western Montana it is found on limestone soils and is
absent or nearly so on granitic and quartzite soils [24].  In the Black
Hills it is confined to calcareous soils developed from limestone parent
material [66]. 

Elevation:  Oregon-grape has a wide elevation range, from near sea level
on the Pacific Coast to 10,000 feet (3,048 m)in the Rocky Mountains
[72].  It is found in high-elevation coniferous forests throughout the
Great Basin [46].  Elevations in Utah range from 4,000 to 9,800 feet
(1,125-2,980 m) [74].

Major overstory associates include ponderosa pine (Pinus ponderosa),
Douglas-fir, grand fir (Abies grandis), quaking aspen (Populus
tremuloides), and western larch (Larix occidentalis).  Major understory
associates include snowberry (Symphoricarpos alba), Rocky Mountain maple
(Acer glabrum), twinflower (Linnaea borealis), blue huckleberry
(Vaccinium globulare), dwarf huckleberry (V. scoparium), and ninebark
(Physocarpus malvaceus) [10].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Oregon-grape is a climax dominant which is shade-tolerant, but also does
well in full sunlight [51].  In the cedar-hemlock (Thuja spp./Tsuga
spp.) zone, it initially responds to open canopies produced by logging,
but begins to decrease within 25 years [75].  Oregon-grape is the
dominant shrub in closed canopy stands of Douglas-fir [61].


SEASONAL DEVELOPMENT : 
In the northern Rocky Mountains Oregon-grape first develops new leaves
from the end of April until late May.  Flowering starts in early May and
may extend to early August.  Fruit ripens from late June until
mid-September [55].  In South Dakota and Nebraska, flowering occurs in
early June, and fruit is ripe by late August [63].

Related categories for Species: Mahonia repens | Oregon-Grape