Development of Polygonum orientale L. grown in competition with maize (Zea mays L.)

Several infestations of Polygonum orientale L. have been observed since 1995 in North-west Italian maize fields. An experiment was carried out in 1997 to study the growth of this species grown in competition with maize. P. orientale plants were transplanted between maize rows, at 2 plants m(-2) density. During the growth, the plant height, number and area of the leaves, length and number of branches, number of inflorescences and dry matter df the different portions were assessed at 20, 30, 40, 55 and 70 days after transplanting. P. orientale reached a maximum height of 147 cm at 70 DAT (days after transplanting). At the end of the experimental period, the number of leaves and inflorescences per plant grew to 38.5 and 45.5, respectively. Inflorescences appeared starting from 40 DAT. The leaf area per plant increased constantly during the first 55 days, reaching 2,194 cm(2). The area of each leaf was strongly related with the length, width and position on the branch. The branches showed a very high range of length, with maximum values for the stem. The dry biomass of epigean portions increased during all the considered periods, and was allocated mainly in the branches.