The influences of indole-3-butyric acid (IBA) concentrations of 0–30 mg·g−1 on the success and speed of adventitious root development of Zamia furfuracea L.f. and Zamia integrifolia L.f. stem cuttings were determined. Root formation success for both species was greater than 95%. The IBA concentrations did not influence the speed of root development for Z. furfuracea, but the Z. integrifolia cuttings that received IBA concentration of 3 mg·g−1 generated adventitious roots more slowly than the cuttings in the control group. The ending dry weights of the stems, leaves, and roots were not influenced by IBA concentration for either species. Our results indicated that adventitious root formation on stem cuttings of these two Zamia species is successful without horticultural application of IBA. Additional IBA studies are needed on the other 300+ cycad species, especially those that are in a threatened category.