The aim of this study was to establish the mechanisms underpinning the observations made in a field trial that suggested that a novel surfactant treatment could promote bentgrasses (Agrostis spp.) in golf greens that contain annual meadow grass (Poa annua L.). Assessments of the effects of three surfactant treatments (named Treatments 1, 2, and 3) on shoot height, biomass accumulation, rhizosheath properties, soil water distribution, and rooting characteristics were made over the course of two experiments carried out under controlled conditions. We found that the leaf extension rate was significantly affected in the two grass species to different extents, depending on the surfactant used. This finding could have positive implications for turf quality in the field for a newly developed formulation (Treatment 3), which was observed to be the case in the field trial that pre-dated this study. The same treatment also resulted in significant differences in the grasses in terms of rhizosheath size compared with untreated soil. We found that surfactants affected the distribution of water in the soil by increasing the rhizosheath water content to bulk soil water content ratio, potentially maximizing water and nutrient uptake by the roots. The combination of effects observed with use of the novel surfactant treatment may lead to improved water use efficiency and a more desirable sward composition for golf greens.