Since their inception in the 1970s, architectural tree models (Hallé et al. 1978) have provided the dominant framework for describing tree forms. An architectural tree model is viewed as a “genetic blueprint” of tree development: a precise developmental pattern subject to disruptive modifications by the environment (Hallé et al. 1978, p. 74): Organization in plants reflects the precisely controlled genetic program, which determines their development. [...] This program is disrupted by exogenous, environmental factors.” On the basis of extensive field data, Halle, Oldeman and Tomlinson distinguished 23 such programs and postulated that they capture the diversity of trees observed in nature. An alternative perspective of tree form was proposed by Sachs and Novoplansky (1995). They viewed environmentally-mediated interactions – in particular, competition between buds and branches for light and space – not merely as a modifier, but as a key determinant of tree form. According to their perspective, genetic and molecular mechanisms do not define tree forms directly, but only set up the rules for tree self-organization through competition between branches (Sachs and Novoplansky 1995): “The form of a tree is generated by self-organization in which alternative branches compete with one another, following no strict plan or pre-pattern.” In spite of the apparent dichotomy between both views, Sachs and Novoplansky postulated that architectural models and self-organization have a complementary character and the diversity of tree forms in nature results from an interplay between them. Here in this thesis I examine the concepts of architectural models, self-organization, and their synthesis in light of computer models implementing these paradigms. In particular, among the results is presented a theoretical morphospace constructed by only a small number of model parameters that captures major characteristics of most of the architectural models. Hallé, F., Oldeman, R. A., & Tomlinson, P. B. (1978). Tropical trees and forests. Berlin: Springer-Verlag. Sachs, T., & Novoplansky, A. (1995). Tree from: Architectural models do not suffice. Israel Journal of Plant Sciences 43, 203–212.