Both in the natural ecological system and in agricultural system, plant debris in soil may significantly influence the physical and chemical features of soil that consequently affect the plant growth. American ginseng (Panax quinquefolium L.), a member of Panax genus, as a highly valuable perennial herb for its medicinal properties, was cultivated with serious continuous cropping problem in cultivating places. The objectives of the study were to determine the effects of degraded annually-maintained root tissues in soil on plant growth and the influence of the postharvest root debris left in soil on the development of continuous American ginseng system. This study used the 3-year old American ginseng seedlings planted in solution and in soil mixed with ground root pieces as simulated root litter to determine their effects on plant growth. Then the effects of root litter on the growth of American ginseng were measured in the hydroponic and field cultural condition respectively. Based on previous studies, this study used nutrient solution amended with 0.02 mg, 0.1 mg, 0.5 mg American ginseng root debris per mL of solution. The plant growth data were collected every 5 days starting from mixing root debris in the solution including expansion of leaves, plant height, canopy growth and etc. The biomass of above and under ground parts were measured at seedling leaf expansion, blooming and fruit set stages. Potted soil was added with 0.1 mg root debris pieces per gram of soil. The measurements of leaf expansion, plant height, canopy growth and etc were conducted every month after planting date. The biomass of above and under ground parts at leaf expansion, blooming and fruit set stages were measured. American ginseng bulk soil samples were collected 30 days after planting date, their phenolic allelochemical contents were determined using high performance liquid chromatography (HPLC). The results showed that in the nutrient solution mixed with 0.02-0.5 mg/mL root debris, the growth of above-ground part of American ginseng were inhibited, leaf expansion was delayed, and the biomass was significantly reduced by 14.9%-45.0% in fruit set stages. The growth of root system was promoted also in such solutions (P<0.05) only during the leaf expansion period. Comparatively, for the potted plants, soil mixed with 0.1 mg/g of root debris also delayed the leaf expansion, plant biomass in both above and under ground parts were all greater than those of the non-debris control. Besides, the results also showed that some phenolic allelochemical contents in the American ginseng bulk soil, such as syringic acid, vanillin, p-coumaric acid, ferulic acid, were decreased by 49.1%-81.4%. However, the salicylic acid content in the treated soil, a stress-induced signal substance in many plants, was increased by 59.9% compared to the control group. In this study, we concluded that the American ginseng root debris had both effects on the inhibiting the growth of above-ground plants and promoting growth of American ginseng roots. This inhibiting effect consequently resulted in a significant decrease in biomass production. However, in the field soil, the degradation rate and the soil adsorption of the root decomposition might reduce the autotoxicity of roots, leading to the effects on growth promotion more significant.