Does Climate Change Alter Weed Management Recommendations? Evaluating the Impact of Elevated CO 2 on Plant Growth and the Critical Period of Weed Control

ABSTRACT Climate change challenges crop production, driving rising temperatures and extreme weather events. Additionally, increased atmospheric CO 2 alters competitive dynamics between crops and weeds. While previous research has examined individual plant responses to elevated CO 2 , its direct impact on weed management recommendations remains understudied. To address this knowledge gap, we assessed how elevated CO 2 influences the critical period of weed control (CPWC). Using radish ( Raphanus sativus L.) as a model crop with dual use of above‐ and belowground parts for consumption and Fagopyrum esculentum Moench (buckwheat) as a model weed, we conducted growth chamber experiments evaluating CO 2 driven shifts in plant growth and CPWC duration. Elevated CO 2 increased radish root biomass while shoot biomass remained relatively unchanged. In contrast, F. esculentum exhibited greater aboveground biomass allocation under elevated CO 2 , while belowground biomass was unaffected. As a result, CPWC shifts under elevated CO 2 depended on the harvested plant part. For radish root yield, CPWC decreased by 93.46 growing degree days suggesting less time is required to manage weeds to sustain yields. Conversely, for radish leaf yield, CPWC increased by 114.14 growing degree days, requiring a longer weed‐free period. These findings suggest that CO 2 driven shifts in biomass allocation could alter CPWC and weed management timing. Understanding these changes is critical for developing adaptive, climate‐resilient weed management strategies.