Abstract:
Devil's club (Oplopanax horridum (J. E. Smith) Miq.) is an indigenous shrub of the Pacific Northwest, often found in the Tsuga heterophylla (western hemlock)/Devil' s club association in western Oregon. In the same family as ginseng, Devil's club is gaining attention for its medicinal properties. While
traditional uses of Devil's club are well known, little biological research on the plant has been documented. This study is intended to increase the ecological knowledge of Devil's club in western Oregon, and provide an ecological basis for developing conservation guidelines. Devil's club's ecological niche, adaptive limitations and growth patterns were studied in the Oregon Cascade Mountains and Oregon Coast Range. Devil's club sub-populations in western Oregon typically grow as patches in canopy gaps. The ecological niche of Devil's club is best characterized as shaded, moist and riparian. Although Devil's club was observed growing throughout a wide range of light environments, its highest micro-site percent cover value occurred in a low-light
environment of 0.05 DIFN (diffuse non-interceptance). Soil moisture averaged
56.8% on a dry weight basis, ranging from 36.3% to 82.2%. Common overstory tree associates include western hemlock, Alnus rubra (red alder), and Pseudotsuga menziesii (Douglas-fir); common understory shrub associates include Rubus spectabilis (salmonberry), Vaccinium sp. (huckleberry) and Acer circinatum (vine maple). Devil's club stem complexes maintain a multiple-aged distribution of stems. A negative correlation between elevation and stem elongation suggests length of growing season limits potential annual stem elongation rates. Measurements of past and current stem branching patterns showed that occupation of growing sites is achieved primarily through layering of aerial stems. There were no observations of Devil's club producing rhizomes or root sprouts, and in two field seasons, there were only two observations of Devil's club seedlings. Stem elongation averaged 17.8 cm per year, with the longest growth occurring in low light environments. A
stem lopping experiment in the field found strong apical dominance in vertical, aerial stems; damage to a stem will trigger bud break. A greenhouse experiment with stem cuttings indicates that production of Devil's club rooting stock should not be difficult.
