Senecio linearifolius is an annual or perennial herb that is not native to California.
There is a high risk of this plant becoming invasive in California according to Cal-IPC.
[Wikipedia] Taxonomy: Senecio linearifolius was first formally described by Achille Richard and the description was published in Voyage de Decouvertes de l'Astrolabe. Botanique.[5][6] The specific epithet (linearifolius) means linear leaved.[7] (link added by Mary Ann Machi)
Calflora:
Information on California plants for education, research and conservation,
with data contributed by
public and private institutions and individuals.
[web application]. 2025.The Calflora Database
[a non-profit organization].Available:
https://www.calflora.org/(Accessed: 03/28/2025).