Cyperus kyllingia and Cyperus brevifolius are two types of weeds in Hawaii that look similar but have different effects on turfgrass. In experiments, Cyperus kyllingia reduced turfgrass growth by 50%, while Cyperus brevifolius did not have a significant impact. Chemical analysis showed that Cyperus kyllingia contains compounds that may inhibit turfgrass growth, while Cyperus brevifolius does not have these compounds. This suggests that Cyperus kyllingia may use allelopathy to outcompete turfgrass, making it a useful model for studying this process.