Euphorbia terracina L., also known as terracina spurge, is a Mediterranean Basin perennial that has recently become invasive in southern California and is actively spreading at a virtually exponential rate along coastal areas in Los Angeles County. The National Park Service (NPS) is undertaking measures to treat and control further spread of current populations, but little is known about the plant's ecology and impact on native plant communities. This study reviewed the existing information on E. terracina and investigated populations established in Solstice Canyon in coastal Los Angeles County. Populations of E. terracina were compared in two different habitats in Solstice Canyon: in an open site along an old road and a shaded riparian site subject to past disturbance. Both open-disturbed and shaded sites had high aboveground biomass densities, with the highest density in the open, disturbed site. Sites differed in biomass allocation and specific leaf area (SLA) between sites, with plants at the open site having significantly lower specific leaf area than those at the shaded site. Open site plants also had high SLA compared to native coastal sage scrub species. Euphorbia terracina produces large quantities of seeds that do not show dormancy. Seeds germinated well under low light intensities without mechanical or chemical treatment. Euphorbia terracina possesses numerous traits — success in disturbed sites, phenotypic plasticity, high SLA compared to native species, high reproductive output, and seeds lacking dormancy — that have been associated with invasive species and likely contribute to both its success and the difficulty in treatment and control of established populations.