Ardisia crenata, an evergreen shade-tolerant shrub native to Japan, forms dense monodominant understories in the introduced range, Florida, USA, unlike its typically ＜＜ 1% cover in Japan. Lack of leaf herbivores or seed predators in Japan implies that the soil may contain pathogens that keep the population density low. This research was to examine soil microbial effects of forest soils in Japan on seedling mortality and relative growth rate (RGR) of Florida ecotype (the invading cultivar in Florida) and Miyazaki ecotype (the representative of Japanese wild genotype). The soil used as soil inoculum was collected from the rhizosphere of wild individuals of A. crenata in forests in Miyazaki and Kyoto, Japan. Seedlings were grown singly in plastic cups filled with sterilized soil medium and either live or autoclave-sterilized soil (10.5% of the soil volume) in a glasshouse for five months. Only the seedlings receiving live soil inoculum showed mortality in both ecotypes, and the Florida ecotype had higher mortality than the Miyazaki ecotype with live soil treatment. RGR showed no effect of either inoculum treatment or ecotype. The results indicate that the soil in Japan contains deleterious pathogens that kill A. crenata seedlings but may not affect seedling growth rate.