Senecio

Senecio /sɪˈniːʃi.oʊ/is a genus of the daisy family (Asteraceae) that includes ragworts and groundsels. The scientific Latin genus name, Senecio, means 'old man.' Variously circumscribed taxonomically, the genus Senecio is one of the largest genera of flowering plants. The traditional circumscription of Senecio is artificial, being polyphyletic, even in its new circumscription which is based on genetic data. Despite the separation of many species into other genera, the genus still contains c. 1,250 species and is one of the largest genera of flowering plants. As no morphological synapomorphies are known to determine which species belong to the genus or not, no exact species numbers are known. The genus has an almost worldwide distribution and evolved in the mid- to late Miocene. Some species produce natural biocides (especially alkaloids) to deter or even kill animals that would eat them. Senecio species are used as food plants by the larvae of some Lepidoptera species — see list of Lepidoptera that feed on Senecio.Pyrrolizidine alkaloids have been found in Senecio nemorensis and in Senecio cannabifolius var. integrilifolius. The flower heads are normally rayed with the heads borne in branched clusters, and usually completely yellow, but green, purple, white and blue flowers are known as well. In its current circumscription, the genus contains species that are annual or perennial herbs, shrubs, small trees, aquatics or climbers. The only species which are trees are the species formerly belonging to Robinsonia occurring on the Juan Fernández Islands. The genus Senecio is distributed almost worldwide. It is one of the few genera occurring in all five regions with a Mediterranean climate. Furthermore, species are found in mountainous regions, including tropical alpine-like areas. Many genera and the whole tribe are in need of revision. Many species currently placed in the genus need to be transferred to other or new genera, and others have been retransferred to Senecio. In its new delimitation the genus is still not monophyletic.