The frequent impreciseness in the names of the species of the Compositae or Asteraceae family found in the catalogues of crop invading plants, due to the various differentiating characteristics that are in their infl orescences which require the use of magnifying glass or stereoscope microscope, motivated the execution of sampling in 24 crops from all the Andean weather zones including the interAndean valleys of Magdalena and Cauca rivers. The purpose of this study was to make careful descriptions, build a dichotomous key that facilitates the classifi cation of these plants, highlight their medical, dietary, industrial and ecological importance accompanied by illustrations and photos. A hundred and ten species were registered taking into account the most recent nomenclature according to the APGIII classifi cation. This study, especially the botanic key, will be of signifi cant usefulness for the determinations in Colombian Herbariums, the countries of the Andean zone and Central America to where the majority of these species extend to; this will be an important fi eld guide for agronomists, agricultural technicians and biologists who may require the knowledge of these plants. With this study, species Ageratum panamense B.L. Rob. And Pectis swartziana Less are pointed out as fi rst record for Colombia. Highlighting the diverse advantages of these plants, the conception of “grass” is intended to change into arvenses or undesired plants in a specifi c place. The article prioritizes the presentation of the key because it’s going to be of immediate use.