Cyperus rotundus L. is a field weed known in all the Southern States as nut grass. The plant produces rhizomes, tubers, basal bulbs and fibrous roots below ground, and rosettes of leaves, scapes, and umbels above ground. The response of nut grass to moisture is an important factor in field eradication and studies were started in the greenhouse to determine the levels at which the plant showed differential response to soil moisture. The results reported herein constitute part of the data collected. Pear, corn, and lemon plants have been shown to respond to differences in moisture well above the so-called wilting point by Aldrich, Work, and Lewis (1), Davis (2), Loomis (4), and Furr and Taylor (3). The distance from the plant to moisture was also shown by Aldrich et al., Davis, and Furr and Taylor to be a factor in the availability of soil moisture for plant growth. In the experiments cited, growth was measured as the soil moisture was reduced, but because of mechanical difficulties the soil could not be maintained at any one moisture level.