AbstractAlligator weed (Alternanthera philoxeroides) is a notorious invasive alien species worldwide. How to limit its population expansion in terrestrial habitats has long been an intractable problem. To predict growth of alligator weed in local patches, a field planting experiment was performed. Using harvesting data, we established growth models of different growth variables; meanwhile, the allometric relationships of these variables were determined. The growth models of main stem length, biomass, leaf area and patch area all in-creased in an exponential pattern with growth period, and the daily growth rates (%) of main stem length, to-tal biomass, leaf area and patch area were 4.28, 11.27, 11.59 and 8.67, respectively. The result of allometric analysis showed that it was significantly correlated between all the growth variables. The allometric exponent b of shoot mass (x) vs. root mass (y) indicated that the root/shoot ratio decreased with the growth of the plant. From the allometric exponent b of main stem length vs. total biomass and of main stem length vs. leaf area, we could deduce that the total biomass and leaf area increased quadratic relative to main stem length, and in-creased proportionally to patch area. As for variables of biomass vs. leaf area, an isometric relationship was found, i.e. the canopy size kept relatively constant when plant size increased. Based on the relation between leaf area and biomass, leaf area ratio (LAR) and specific leaf area (SLA) of the alligator weed in terrestrial habitat were calculated, being 88.24 cm²/g and 287.97 cm²/g, respectively. These results provide basic data for future growth modeling further to effective and economical control.