The synthesis parameter space of bismuth catalyzed germanium nanowires by chemical vapor deposition is determined. The process window for high aspect ratio nanowires is found to be extremely narrow. The optimal conditions are found to be 300 degrees C and 150 Torr gas pressure. For lower temperatures, the solubility of Ge in Bi is too low for the nucleation of Ge nanowires to occur. For higher temperatures, small Bi droplets tend to evaporate leading to an extreme reduction in the nanowire density. The extremely low process temperature makes Bi a good candidate for its growth on low cost and low thermal budget substrates such as plastics.