Seedlings of Lolium multiflorum Lam., Lespedeza stipulacea Maxim., and Buteloua curtipendula (Michx.) Torr. were grown for 48 hours in darkness at constant temperatures of 22°, 27°, 32°, or 37°C either in distilled water or polyethylene glycol 20,000 (PEG) solutions with osmotic potentials of −3.2, −7.7, and −9.8 bars. Redicle growth rate decreased as concentrations of polyethylene glycol increased. Radicle growth was reduced at 32° and negligible at 37° for L. multiflorum. All levels of PEG-induced osmotic stress reduced radicle growth at 22° and 32°, while at 27° only higher levels reduced growth of L. multiflorum. PEG-induced osmotic stress reduced radicle growth of B. curtipendula significantly at all temperatures except 37°, where the lowest level of PEG had an insignificant effect on radicle growth. With L. stipulacea, low levels of PEG-induced osmotic stress did not have a significant effect on radicle growth, but an osmotic stress of −9 bars reduced growth at all temperatures.