Technical Abstract: Methods for in vitro induction of polyploid Cercis glabra Pamp. using oryzalin were developed and evaluated. Methods included treating shoot or callus cultures for different exposure durations with either an aqueous solution of 150 µM oryzalin or by inclusion of oryzalin into solidified culture media. Polyploidy induction by the various oryzalin treatments was assayed by measuring nuclei DNA content using flow cytometry. Results indicate that treating either apical or lateral buds from in vitro shoot cultures with an aqueous solution of oryzalin for 12 to 96 hours produced tetraploid plants irrespective of the type of bud treated. In contrast, shoots cultured on the solidified media containing oryzalin failed to produce polyploid nuclei. Using aqueous treatments of oryzalin and shoot cultures polyploid Cercis glabra plants were successfully rooted and produced. Although an increase in the frequency of polyploidy nuclei was detected in callus cultures grown on media containing orzyalin, these treatments significantly reduced callus growth and viability. Results from this study indicate that aqueous treatment of in vitro grown shoot cultures may provide an efficient and simple method for the generation of polyploidy plants.