Blumea axillaris (Inuleae, Asteraceae): the first record of an invasive exotic weed in the Americas and the first record of the genus in Brazil

Blumea is one of the largest genus within the tribe Inuleae, Asteraceae, with approximately 100 species across tropical Asia, Africa, Oceania, and the Americas. It is characterized by disciform capitula, one large oxalate crystal in each cypsela epidermis cell, radial anther endothecium thickenings, and tailed anthers. There are no native species of Blumea in the Americas and Hawaii. However, two species have been documented, and both were introduced. Thus, this work documents the first records of Blumea axillaris in the Americas and the first report of this genus in Brazil. We provided a morphological description of the species, with ecological observations, a key for identifying the Blumea among the genera of the tribe Inuleae found in Brazil, and illustrations. This record serves as a warning since it is an invasive exotic species that, by all indications, has already firmly established itself as a weed and can represent significant challenges for agriculture and the environment.