while CTAB-capped seeds are single crystalline, hence the former lead to bipyramids and the latter lead to rods. The first decision boundary in the decision tree divides the dataset into recipes that use CTAB as the seed capping agent leading to rods and cubes, and recipes that use other capping agents (including citrate+BH bipyramids). This is consistent with the prior study that adding HCl in growth solution slows the reaction rate allowing growth of more anisotropic shapes. The third decision regards AuCl - 4 in seed solution. Although this decision is made with very little support for bipyramids and we could not find a direct statement related to this decision, Langille et al. reviewed that the growth of gold nanostars is promoted by rapid kinetic growth. Higher pH in growth solution and higher concentration of AuCl - 4 in seed solution could be in line with fast growth rate.