A survey of weeds growing in rice crops in the State of Sao Paulo was conducted. The life cycle, size, phenology and mode of reproduction of each of the collected species were studied. The herbaceous growth, annual life cycle, blooming and fructification during the warmest months of the year and dissemination by seeds were mainly predominant for the studied species. From the 15 dicotyledoneous families observed with a to tal of 31 identified species, three were quantitatively more important: Compositae, Malvaceae and Amaranthaceae. A toxonomical key was written for those genera with more than one species in an attempt to help identification in the first growth stage. All the scientific and common names and when possible, the etimology of the genera or species are included. In order to facilitate the keying and classification of seedlings from each of the studied species, a description and a drawing are provided.
Survey; weeds rice; biologic