Potassium content of turfgrass leaves is usually reported on a dry weight basis as g K kg^-1 dry matter (K_D). By measuring tissue water content (TWC), K can alternatively be expressed as mmol K L^-1 (K_W). We compared K_D to K_W in creeping bentgrass [Agrostis stolonifera var. palustris (Huds.) Farw.] tissue samples collected from field- and greenhouse-grown plants that were treated with varying rates of K fertilizer, grown in sand rootzones of differing exchangeable K content, and allowed to vary in TWC. A generally accepted sufficiency range of K_D is (15 to 30 g kg^-1), and K_W may need to be maintained above 80 mmol L^-1 to meet the biochemical K requirement, with additional K contributing to the biophysical demand for K. We found that in a range of K_D from 5 to 25 g kg^-1, the K_W ranged from about 50 to 230 mmol L^-1. However, samples with K_D below 15 g kg^-1 often had K_W above 150 mmol L^-1. Increasing TWC is associated with lower K_W and higher K_D. It appears that much of the variability in K_D can be explained by TWC, and the sufficiency ranges for creeping bentgrass K content may be more physiologically meaningful if they are based on K_W rather than K_D.