We propose a real-time interactive system that enables users to generate, manipulate and edit the shape model of a tree based on growth simulation by directly indicating its global and spatial information. For this purpose, three-dimensional (3D) spatial information is introduced to the well-known Lsystem as an attribute of the growth simulation. Moreover, we propose an efficient data structure of L-strings in order to speed up the process. Keywords Virtual reality, Multimodal interface, Intuitive interaction, L-system, Tree models, Data structure