Resumo. Architectural models contribute to describe the development and the arrangement of the tree canopy. This knowledge is crucial for the understanding of the behavior of forest trees and it may also help us understand the evolutionary relationships among the taxa. This study is aimed at identifying how rich the architectural models of the arboreal species of a seasonal forest are. The data was gathered from field observations and specialized literature. It presents a list of 53 tree species from the tree flora of the Subtropical Seasonal Forest of the Santa Maria - RS, distributed in 45 genera and 28 families in the tree flora. A total of 13 different architectural models have been recognized. The most prominent models were Rauh, Troll, Scarrone, Roux and Massart. The architectural complexity, reflected by the high number of models described, is due to the development of the canopy in the rest of the study. This work had a pioneering and exploratory character and shall provide a framework for new studies on plant architecture in the subtropical region of Brazil.