Abstract: Catchweed bedstraw, common hempnettle, wild buckwheat, and wild oat are serious competitors to arable crops in many parts of the world where cutting implements may be used to control weeds. After cutting, regrowth may become a problem. In greenhouse experiments, weed species were cut at different stages of development (wild oat had two or three leaves, and the dicot weed species were 10 or 15 cm high) and at different heights aboveground (5 and 8 cm). Three weeks after sowing, biomass was measured and compared with that of uncut plants. Cutting height had a significant effect on the regrowth of all species. Common hempnettle was the most sensitive to cutting height followed by wild oat, wild buckwheat, and catchweed bedstraw. Increasing cutting height from 5 to 8 cm above the soil surface increased biomass production by 100 to 400% for all species. Cutting catchweed bedstraw at 8 cm resulted in larger biomass production than that of uncut plants (about 30%). For this species, weed control by cutting once in the growing season, 8 cm aboveground, may result in increased weed biomass production when compared with no cutting. The stage of development when the plants were cut did not have a significant effect on the regrowth ability of any of the species, probably because the two growth stages were relatively close in time.
Nomenclature: Catchweed bedstraw, Galium aparine L. #3 GALAP; common hempnettle, Galeopsis tetrahit L. # GAETE; wild buckwheat, Polygonum convolvulus L. # POLCO; wild oat, Avena fatua L. # AVAFA.
Additional index words: Alternative weed control, compensatory growth, mechanical weed control, mowing, overcompensation, ranking weeds.