[Wikipedia] Taxonomy: The genus is named after the English naturalists and explorers John Tradescant the Elder (c. 1570s - 1638) and John Tradescant the Younger (1608 - 1662). (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).