Description
American barberry is a sparsely branched shrub, 0.3-2 m tall with forked or trifid spines on its branches. Branchlets are brown, purple or reddish and rough-warty. The leaves are obovate to spatulate, 2-6 cm long, with non-distinct veinlets below, margins with up to 20 teeth, with thorns. The 5-10 flowers are in racemes up to 2-6 cm long. Flower petals are yellow, notched, 2.5-3.5 mm long with basal glands. The calyx is 8-11 mm wide with inner sepals 3-4 mm long. Fruits are ovoid, fleshy, scarlet berries, 5-7 mm long. (Gleason and Cronquist 1991, Mohlenbrock 1975).
Habitat
Berberis canadensis occurs in open woods, on bluffs and cliffs and along river banks in the eastern and central United States (Gleason and Cronquist 1991, Cook et al. 1987, Fernald 1970, Small 1933). Formerly an inhabitant of savannas and open woodlands, fire suppression has significantly restricted its habitat to sites with shallow soil (such as glades and cliffs) or areas with mowing or other canopy-clearing activities (such as powerline corridors, railroad/road right-of-ways and riverbanks).
The single extant population from Indiana is restricted to steep banks along the Tippecanoe River in the northern part of the state (Homoya 1992). Associated plant species include Besseya bullii, Lithospermum sp. and liverworts (Indiana Natural Heritage Data Center 1989).
Historically, B. canadensis occurred in Maryland in dry, calcareous woodlands, open fields and serpentine barrens (Maryland Natural Heritage Program 1992).
In Missouri, B. canadensis is typically found on north-facing, rocky, wooded slopes; along streams; upper ledges or bluffs; exposed upper portions of bluffs on limestone, dolomite or sandstone; and mesic limestone/dolomite cliffs (Smith 1992, Roedner et al. 1978, Holt et al. 1974, University of Minnesota Herbarium (MIN)). Substrate composition usually consists of limestone, dolomite or sandstone with a somewhat basic pH (Smith 1993). Steyermark (1963) stated that the plant appears to be restricted to the edges of limestone bluffs where the soil is leached out, or near the contact point between chert or Roubidoux sandstone with limestone. Associated plant species in Missouri include Campanula rotundifolia, Carpinus caroliniana, Galium boreale ssp. septentrionale, Trautvetteria caroliniensis, and Zigadenus elegans (Smith 1992, Steyermark 1963).
Berberis canadensis is found in 19 mountain counties in southwest Virginia (Huber 1993). Occupied habitat includes dry, open woodlands over limestone, dolomite, richer sandstone or shale substrates, rocky and cliffy areas and open areas and glades with naturally thin soil (Ludwig 1993, Ludwig 1992). Associated plant species in glades include Helianthus divaricatus, Juniperus virginiana, and Schizachyrium scoparium. In rocky areas it is found with Cercis canadensis, Pellaea atropurpurea, and Quercus muehlenbergii (Ludwig 1993).
In North Carolina, B. canadensis occurs in the Piedmont on mafic rocks (such as diabase, amphibolite and gabbro) and in the Blue Ridge on calcareous (limestone, dolomite, marble) and mafic rocks (amphibolite). It generally occurs in glade, open woodland, bluff or cliff situations (North Carolina Natural Heritage 1993, Weakley 1993, University of Minnesota Herbarium (MIN)). The species was historically found in fire-maintained habitats which kept the canopy open, but is now restricted to sites with very shallow soil or with mowing maintenance (right-of-ways, powerline corridors, etc.). Due to its association with mafic and calcareous rocks (uncommon to rare in the state), B. canadensis is often associated with other rare species. Typical associated plant species include Aquilegia canadensis, Cercis canadensis, Clematis ochroleuca, Desmodium spp., Echinacea laevigata, Matelea decipiens, Parthenium auriculatum, Pycnanthemum spp., Rhus aromatica, Silphium trifoliatum, Solidago rigida, Symphoricarpos orbiculatus, and Viburnum rafinesquianum (North Carolina Natural Heritage 1993, Weakley 1993).
In Illinois, B. canadensis is known from a single extant site at the rim of a dry sandstone cliff (Illinois Natural Heritage Division 1992).
Collections at the University of Tennessee-Knoxville Herbarium (TENN) suggest that occupied habitat is relatively open woodlands (Pyne 1994). Collections have been made from wooded slopes, shale slopes, bluffs, terraces along river bluffs and river banks.