Responses to drought were studied on greenhouse grown plants of Sphaeralcea grossulariaefolia (Hook. & Arn.) Rydberg. A pressure bomb was modified to measure leaf water potential (ψ). Leaf water potentials varied from -2 to -80 bars. Matric potential proved negligible. Low osmotic potentials indicated that turgor pressure remained positive. Photosynthesis decreased linearily with leaf water potential decreases. At about -32 bars ψ net photosynthesis became zero and around -45 bars ψ all photosynthesis ceased. Dark respiration decreased below about -18 bars proportionally to leaf water potential decrease until becoming minute at -60 bars. A very rapid rise in CO2 equilibrium concentration occurred as leaf water potential decreased below -18 bars. Abscission of leaves began at -6 bars ψ. At -32 bars ψ only about 15 percent of initial leaf area remained. A close balance between transpiration and soil moisture absorption was maintained by stomatal closure and leaf area abscission. Upon watering, rapid regeneration of foliage following severe drought was especially notable. Growth characteristics related to drought and possible indexes of physiological vitality were discussed.