Abstract: Polygonum lapathifolium L. is a morphologically variable and taxonomically complicated group. The height of plants and the degree of nodal expansion greatly vary in different habitats. In this work field observation and mass collection in different habitats of this species were made. By means of biometric techniques, principal component analysis, discriminant analysis, scatter diagram and histogram, supplemented by transplantation experiment, it is revealed that the height of plants and the degree of nodal expansion of P. lapathifolium are evidently affected by environmental conditions, and these two variables are not correlated with, but independent from, each other. The results also show that the indumentum on the lower leaf surface is not constant. Therefore all the characters are not reliable diagnostic ones and any taxonomic treatment based on these characters is not reasonable. In this paper, P. nodosum Pers. is reduced as a synonym of P. lapathifolium L. and P.lapathifolium var. salicifolium Sibth. is also eliminated.

Key words: Polygonum lapathifolium L., P. nodosum Pers, Character analysis