The autointoxication of chrysanthemum was studied using water extract of Dendranthema morifolium's rhizospheric soil. Results of bioassays showed that the water extract inhibited chrysanthemum seed germination and the activities of some important root enzymes. The seedling nitrate reductase activity was decreased linearly with increasing concentration of the extract. The activity of root dehydrogenase was inhibited only at the highest concentration tested [3.2 g·mL-1, dry weight (DW)], but was stimulated at a lower concentration tested (1.6 g·mL-1, DW). Malondialdehyde content increased at higher than 1.6 g·mL-1, DW concentrations of the extract. The autointoxication phenomenon might be related to the difficulties in continuous plantings of chrysanthemum at the same location.