Fallopia japonica [Reynoutria japonica] is an invasive exotic species that spreads by an extensive rhizome system, but does not reproduce by seed outside of its native range. Greenhouse experiments explored the effectiveness of cutting as a control measure. Patterns of biomass allocation to above- and below-ground portions of uncut plants over a growing season were monitored, and cutting experiments were performed to determine the effects on below-ground biomass of cutting, timing of cutting, time interval between cuts, and multiple cuts. The allocation to below-ground biomass was continuous during the growing season, with the total below-ground biomass exceeding the above-ground biomass in the latter half of the growing season. Cut plants had significantly less below-ground biomass accumulation at the end of the growing season compared to uncut controls. Rhizome biomass at the end of the growing season was inversely related to the number of cuts. With 1, 2, and 3 cuts, below-ground biomass was 65, 31 and 13%, respectively, of uncut controls. Regression analysis predicted that a minimum of 4 cuts are needed during a single growing season to cause a net depletion of below-ground biomass. The timing of cutting does not appear to be critical as long as it is done at least 7 weeks prior to senescence. Given its continuous allocation to rhizomes and its ability to sprout from as little as 7 g of rhizome, it is unlikely that F. japonica can be eradicated by cutting alone.