Green plants' fast rendering and faithful description are a real challenge in computer graphics. How can we faithfully mo del and high efficiently compute green plants' production according to botanical knowledge to adapt to the increasing demand of scientific research, education and business. In this paper, we present a new algorithm to quickly compute the plants' production, and then, for certain plant architectural models, combine with the geometrical rules to create substructure library. Finally, we construct 3D virtual plants using 3D organs. Compared with the classical method in computing and constructing plant structures, the algorithm described in this paper is much faster while keeping accurate shape. The algorithm can be generalized to most plant species.